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- - diff --git a/zkat/fix-stuff/draft-marchan-kdl2.txt b/zkat/fix-stuff/draft-marchan-kdl2.txt deleted file mode 100644 index 5a9f143..0000000 --- a/zkat/fix-stuff/draft-marchan-kdl2.txt +++ /dev/null @@ -1,1246 +0,0 @@ - - - - -KDL Community K. Marchán - Microsoft - KDL Contributors - 23 January 2025 - - - The KDL Document Language - draft-marchan-kdl2-latest - -Abstract - - KDL is a node-oriented document language. Its niche and purpose - overlaps with XML, and as do many of its semantics. You can use KDL - both as a configuration language, and a data exchange or storage - format, if you so choose. - - This is the formal specification for KDL, including the intended data - model and the grammar. - - This document describes an unreleased minor change to KDL. For the - latest oficial version of the language, see https://kdl.dev/spec. - -About This Document - - This note is to be removed before publishing as an RFC. - - Status information for this document may be found at - https://datatracker.ietf.org/doc/draft-marchan-kdl2/. - - information can be found at https://kdl.dev/. - - Source for this draft and an issue tracker can be found at - https://github.com/kdl-org/kdl. - -License - - This work is licensed under Creative Commons Attribution-ShareAlike - 4.0 International. To view a copy of this license, visit - https://creativecommons.org/licenses/by-sa/4.0/ - -Table of Contents - - 1. Compatibility - 2. Introduction - 3. Components - 3.1. Document - 3.1.1. Example - 3.2. Node - 3.2.1. Example - 3.3. Line Continuation - 3.3.1. Example - 3.4. Property - 3.5. Argument - 3.5.1. Example - 3.6. Children Block - 3.6.1. Example - 3.7. Value - 3.8. Type Annotation - 3.8.1. Reserved Type Annotations for Numbers Without Decimals: - 3.8.2. Reserved Type Annotations for Numbers With Decimals: - 3.8.3. Reserved Type Annotations for Strings: - 3.8.4. Examples - 3.9. String - 3.10. Identifier String - 3.10.1. Non-initial characters - 3.10.2. Non-identifier characters - 3.11. Quoted String - 3.11.1. Escapes - 3.12. Multi-line String - 3.12.1. Newline Normalization - 3.12.2. Examples - 3.12.3. Interaction with Whitespace Escapes - 3.13. Raw String - 3.13.1. Example - 3.14. Number - 3.14.1. Keyword Numbers - 3.15. Boolean - 3.15.1. Example - 3.16. Null - 3.16.1. Example - 3.17. Whitespace - 3.17.1. Single-line comments - 3.17.2. Multi-line comments - 3.17.3. Slashdash comments - 3.18. Newline - 3.19. Disallowed Literal Code Points - 4. Full Grammar - 4.1. Grammar language - Authors' Addresses - -1. Compatibility - - KDL 2.0 is designed such that for any given KDL document written as - KDL 1.0 (./SPEC_v1.md) or KDL 2.0, the parse will either fail - completely, or, if the parse succeeds, the data represented by a v1 - or v2 parser will be identical. This means that it's safe to use a - fallback parsing strategy in order to support both v1 and v2 - simultaneously. For example, node "foo" is a valid node in both - versions, and should be represented identically by parsers. - - A version marker /- kdl-version 2 (or 1) _MAY_ be added to the - beginning of a KDL document, optionally preceded by the BOM, and - parsers _MAY_ use that as a hint as to which version to parse the - document as. - -2. Introduction - - KDL is a node-oriented document language. Its niche and purpose - overlaps with XML, and as do many of its semantics. You can use KDL - both as a configuration language, and a data exchange or storage - format, if you so choose. - - The bulk of this document is dedicated to a long-form description of - all Components (Section 3) of a KDL document. There is also a much - more terse Grammar (Section 4) at the end of the document that covers - most of the rules, with some semantic exceptions involving the data - model. - - KDL is designed to be easy to read _and_ easy to implement. - - In this document, references to "left" or "right" refer to directions - in the _data stream_ towards the beginning or end, respectively; in - other words, the directions if the data stream were only ASCII text. - They do not refer to the writing direction of text, which can flow in - either direction, depending on the characters used. - -3. Components - -3.1. Document - - The toplevel concept of KDL is a Document. A Document is composed of - zero or more Nodes (Section 3.2), separated by newlines, semicolons, - and whitespace, and eventually terminated by an EOF. - - All KDL documents MUST be encoded in UTF-8 and conform to the - specifications in this document. - -3.1.1. Example - - The following is a document composed of two toplevel nodes: - - foo { - bar - } - baz - -3.2. Node - - Being a node-oriented language means that the real core component of - any KDL document is the "node". Every node must have a name, which - must be a String (Section 3.9). - - The name may be preceded by a Type Annotation (Section 3.8) to - further clarify its type, particularly in relation to its parent - node. (For example, clarifying that a particular date child node is - for the _publication_ date, rather than the last-modified date, with - (published)date.) - - Following the name are zero or more Arguments (Section 3.5) or - Properties (Section 3.4), separated by either whitespace - (Section 3.17) or a slash-escaped line continuation (Section 3.3). - Arguments and Properties may be interspersed in any order, much like - is common with positional arguments vs options in command line tools. - Collectively, Arguments and Properties may be referred to as - "Entries". - - Children (Section 3.6) can be placed after the name and the optional - Entries, possibly separated by either whitespace or a slash-escaped - line continuation. - - Arguments are ordered relative to each other and that order must be - preserved in order to maintain the semantics. Properties between - Arguments do not affect Argument ordering. - - By contrast, Properties _SHOULD NOT_ be assumed to be presented in a - given order. Children (Section 3.6) should be used if an order- - sensitive key/value data structure must be represented in KDL. Cf. - JSON objects preserving key order. - - Nodes _MAY_ be prefixed with Slashdash (Section 3.17.3) to "comment - out" the entire node, including its properties, arguments, and - children, and make it act as plain whitespace, even if it spreads - across multiple lines. - - Finally, a node is terminated by either a Newline (Section 3.18), a - semicolon (;), the end of its parent's child block (}) or the end of - the file/stream (an EOF). - -3.2.1. Example - - // `foo` will have an Argument value list like `[1, 3]`. - foo 1 key=val 3 { - bar - (role)baz 1 2 - } - -3.3. Line Continuation - - Line continuations allow Nodes (Section 3.2) to be spread across - multiple lines. - - A line continuation is a \ character followed by zero or more - whitespace items (including multiline comments) and an optional - single-line comment. It must be terminated by a Newline - (Section 3.18) (including the Newline that is part of single-line - comments). - - Following a line continuation, processing of a Node can continue as - usual. - -3.3.1. Example - - my-node 1 2 \ // comments are ok after \ - 3 4 // This is the actual end of the Node. - -3.4. Property - - A Property is a key/value pair attached to a Node (Section 3.2). A - Property is composed of a String (Section 3.9), followed immediately - by an equals sign (=, U+003D), and then a Value (Section 3.7). - - Properties should be interpreted left-to-right, with rightmost - properties with identical names overriding earlier properties. That - is: - - node a=1 a=2 - - In this example, the node's a value must be 2, not 1. - - No other guarantees about order should be expected by implementers. - Deserialized representations may iterate over properties in any order - and still be spec-compliant. - - Properties _MAY_ be prefixed with /- to "comment out" the entire - token and make it act as plain whitespace, even if it spreads across - multiple lines. - -3.5. Argument - - An Argument is a bare Value (Section 3.7) attached to a Node - (Section 3.2), with no associated key. It shares the same space as - Properties (Section 3.4), and may be interleaved with them. - - A Node may have any number of Arguments, which should be evaluated - left to right. KDL implementations _MUST_ preserve the order of - Arguments relative to each other (not counting Properties). - - Arguments _MAY_ be prefixed with /- to "comment out" the entire token - and make it act as plain whitespace, even if it spreads across - multiple lines. - -3.5.1. Example - - my-node 1 2 3 a b c - -3.6. Children Block - - A children block is a block of Nodes (Section 3.2), surrounded by { - and }. They are an optional part of nodes, and create a hierarchy of - KDL nodes. - - Regular node termination rules apply, which means multiple nodes can - be included in a single-line children block, as long as they're all - terminated by ;. - -3.6.1. Example - - parent { - child1 - child2 - } - - parent { child1; child2 } - -3.7. Value - - A value is either: a String (Section 3.9), a Number (Section 3.14), a - Boolean (Section 3.15), or Null (Section 3.16). - - Values _MUST_ be either Arguments (Section 3.5) or values of - Properties (Section 3.4). Only String (Section 3.9) values may be - used as Node (Section 3.2) names or Property (Section 3.4) keys. - - Values (both as arguments and in properties) _MAY_ be prefixed by a - single Type Annotation (Section 3.8). - -3.8. Type Annotation - - A type annotation is a prefix to any Node Name (Section 3.2) or Value - (Section 3.7) that includes a _suggestion_ of what type the value is - _intended_ to be treated as, or as a _context-specific elaboration_ - of the more generic type the node name indicates. - - Type annotations are written as a set of ( and ) with a single String - (Section 3.9) in it. It may contain Whitespace after the ( and - before the ), and may be separated from its target by Whitespace. - - KDL does not specify any restrictions on what implementations might - do with these annotations. They are free to ignore them, or use them - to make decisions about how to interpret a value. - - Additionally, the following type annotations MAY be recognized by KDL - parsers and, if used, SHOULD interpret these types as follows: - -3.8.1. Reserved Type Annotations for Numbers Without Decimals: - - Signed integers of various sizes (the number is the bit size): - - * i8 - - * i16 - - * i32 - - * i64 - - * i128 - - Unsigned integers of various sizes (the number is the bit size): - - * u8 - - * u16 - - * u32 - - * u64 - - * u128 - - Platform-dependent integer types, both signed and unsigned: - - * isize - - * usize - -3.8.2. Reserved Type Annotations for Numbers With Decimals: - - IEEE 754 floating point numbers, both single (32) and double (64) - precision: - - * f32 - - * f64 - - IEEE 754-2008 decimal floating point numbers - - * decimal64 - - * decimal128 - -3.8.3. Reserved Type Annotations for Strings: - - * date-time: ISO8601 date/time format. - - * time: "Time" section of ISO8601. - - * date: "Date" section of ISO8601. - - * duration: ISO8601 duration format. - - * decimal: IEEE 754-2008 decimal string format. - - * currency: ISO 4217 currency code. - - * country-2: ISO 3166-1 alpha-2 country code. - - * country-3: ISO 3166-1 alpha-3 country code. - - * country-subdivision: ISO 3166-2 country subdivision code. - - * email: RFC5322 email address. - - * idn-email: RFC6531 internationalized email address. - - * hostname: RFC1123 internet hostname (only ASCII segments) - - * idn-hostname: RFC5890 internationalized internet hostname (only xn - ---prefixed ASCII "punycode" segments, or non-ASCII segments) - - * ipv4: RFC2673 dotted-quad IPv4 address. - - * ipv6: RFC2373 IPv6 address. - - * url: RFC3986 URI. - - * url-reference: RFC3986 URI Reference. - - * irl: RFC3987 Internationalized Resource Identifier. - - * irl-reference: RFC3987 Internationalized Resource Identifier - Reference. - - * url-template: RFC6570 URI Template. - - * uuid: RFC4122 UUID. - - * regex: Regular expression. Specific patterns may be - implementation-dependent. - - * base64: A Base64-encoded string, denoting arbitrary binary data. - - * base85: An Ascii85 (https://en.wikipedia.org/wiki/Ascii85)-encoded - string, denoting arbitrary binary data. - -3.8.4. Examples - - node (u8)123 - node prop=(regex).* - (published)date "1970-01-01" - (contributor)person name="Foo McBar" - -3.9. String - - Strings in KDL represent textual UTF-8 Values (Section 3.7). A - String is either an Identifier String (Section 3.10) (like foo), a - Quoted String (Section 3.11) (like "foo") or a Multi-Line String - (Section 3.12). Both Quoted and Multiline strings come in normal and - Raw String (Section 3.13) variants (like #"foo"#): - - * Identifier Strings let you write short, "single-word" strings with - a minimum of syntax - - * Quoted Strings let you write strings "like normal", with - whitespace and escapes. - - * Multi-Line Strings let you write strings across multiple lines and - with indentation that's not part of the string value. - - * Raw Strings don't allow any escapes, allowing you to not worry - about the string's content containing anything that might look - like an escape. - - Strings _MUST_ be represented as UTF-8 values. - - Strings _MUST NOT_ include the code points for disallowed literal - code points (Section 3.19) directly. Quoted and Multi-Line Strings - may include these code points as _values_ by representing them with - their corresponding \u{...} escape. - -3.10. Identifier String - - An Identifier String (sometimes referred to as just an "identifier") - is composed of any Unicode Scalar Value (https://unicode.org/ - glossary/#unicode_scalar_value) other than non-initial characters - (Section 3.10.1), followed by any number of Unicode Scalar Values - other than non-identifier characters (Section 3.10.2). - - A handful of patterns are disallowed, to avoid confusion with other - values: - - * idents that appear to start with a Number (Section 3.14) (like - 1.0v2 or -1em) or the "almost a number" pattern of a decimal point - without a leading digit (like .1). - - * idents that are the language keywords (inf, -inf, nan, true, - false, and null) without their leading #. - - Identifiers that match these patterns _MUST_ be treated as a syntax - error; such values can only be written as quoted or raw strings. The - precise details of the identifier syntax is specified in the Full - Grammar in Section 4. - -3.10.1. Non-initial characters - - The following characters cannot be the first character in an - Identifier String (Section 3.10): - - * Any decimal digit (0-9) - - * Any non-identifier characters (Section 3.10.2) - - Additionally, the following initial characters impose limitations on - subsequent characters: - - * the + and - characters can only be used as an initial character if - the second character is _not_ a digit. If the second character is - ., then the third character must _not_ be a digit. - - * the . character can only be used as an initial character if the - second character is _not_ a digit. - - This allows identifiers to look like --this or .md, and removes the - ambiguity of having an identifier look like a number. - -3.10.2. Non-identifier characters - - The following characters cannot be used anywhere in a Identifier - String (Section 3.10): - - * Any of (){}[]/\"#;= - - * Any Whitespace (Section 3.17) or Newline (Section 3.18). - - * Any disallowed literal code points (Section 3.19) in KDL - documents. - -3.11. Quoted String - - A Quoted String is delimited by " on either side of any number of - literal string characters except unescaped " and \. - - Literal Newline (Section 3.18) characters can only be included if - they are Escaped Whitespace (Section 3.11.1.1), which discards them - from the string value. Actually including a newline in the value - requires using a newline escape sequence, like \n, or using a Multi- - Line String (Section 3.12) which is actually designed for strings - stretching across multiple lines. - - Like Identifier Strings, Quoted Strings _MUST NOT_ include any of the - disallowed literal code-points (Section 3.19) as code points in their - body. - - Quoted Strings have a Raw String (Section 3.13) variant, which - disallows escapes. - -3.11.1. Escapes - - In addition to literal code points, a number of "escapes" are - supported in Quoted Strings. "Escapes" are the character \ followed - by another character, and are interpreted as described in the - following table: - - +==============+=========+=========================================+ - | Name | Escape | Code Pt | - +==============+=========+=========================================+ - | Line Feed | \n | U+000A | - +--------------+---------+-----------------------------------------+ - | Carriage | \r | U+000D | - | Return | | | - +--------------+---------+-----------------------------------------+ - | Character | \t | U+0009 | - | Tabulation | | | - | (Tab) | | | - +--------------+---------+-----------------------------------------+ - | Reverse | \\ | U+005C | - | Solidus | | | - | (Backslash) | | | - +--------------+---------+-----------------------------------------+ - | Quotation | \" | U+0022 | - | Mark (Double | | | - | Quote) | | | - +--------------+---------+-----------------------------------------+ - | Backspace | \b | U+0008 | - +--------------+---------+-----------------------------------------+ - | Form Feed | \f | U+000C | - +--------------+---------+-----------------------------------------+ - | Space | \s | U+0020 | - +--------------+---------+-----------------------------------------+ - | Unicode | \u{(1-6 | Code point described by hex characters, | - | Escape | hex | as long as it represents a Unicode | - | | chars)} | Scalar Value (https://unicode.org/ | - | | | glossary/#unicode_scalar_value) | - +--------------+---------+-----------------------------------------+ - | Whitespace | See | N/A | - | Escape | below | | - +--------------+---------+-----------------------------------------+ - - Table 1 - -3.11.1.1. Escaped Whitespace - - In addition to escaping individual characters, \ can also escape - whitespace. When a \ is followed by one or more literal whitespace - characters, the \ and all of that whitespace are discarded. For - example, - - "Hello World" - - and - - "Hello \ World" - - are semantically identical. See whitespace (Section 3.17) and - newlines (Section 3.18) for how whitespace is defined. - - Note that only literal whitespace is escaped; whitespace escapes (\n - and such) are retained. For example, these strings are all - semantically identical: - - "Hello\ \nWorld" - - "Hello\n\ - World" - - "Hello\nWorld" - - """ - Hello - World - """ - -3.11.1.2. Invalid escapes - - Except as described in the escapes table, above, \ _MUST NOT_ precede - any other characters in a string. - -3.12. Multi-line String - - Multi-Line Strings support multiple lines with literal, non-escaped - Newlines. They must use a special multi-line syntax, and they - automatically "dedent" the string, allowing its value to be indented - to a visually matching level as desired. - - A Multi-Line String is opened and closed by _three_ double-quote - characters, like """. Its first line _MUST_ immediately start with a - Newline (Section 3.18) after its opening """. Its final line _MUST_ - contain only whitespace before the closing """. All in-between lines - that contain non-newline, non-whitespace characters _MUST_ start with - _at least_ the exact same whitespace as the final line (precisely - matching codepoints, not merely counting characters or "size"); they - may contain additional whitespace following this prefix. The lines - in between may contain unescaped " (but no unescaped """ as this - would close the string). - - The value of the Multi-Line String omits the first and last Newline, - the Whitespace of the last line, and the matching Whitespace prefix - on all intermediate lines. The first and last Newline can be the - same character (that is, empty multi-line strings are legal). - - In other words, the final line specifies the whitespace prefix that - will be removed from all other lines. - - Multi-line Strings that do not immediately start with a Newline and - whose final """ is not preceeded by optional whitespace and a Newline - are illegal. This also means that """ may not be used for a single- - line String (e.g. """foo"""). - -3.12.1. Newline Normalization - - Literal Newline sequences in Multi-line Strings must be normalized to - a single U+000A (LF) during deserialization. This means, for - example, that CR LF becomes a single LF during parsing. - - This normalization does not apply to non-literal Newlines entered - using escape sequences. That is: - - multi-line """ - \r\n[CRLF] - foo[CRLF] - """ - - becomes: - - single-line "\r\n\nfoo" - - For clarity: this normalization applies to each individual Newline - sequence. That is, the literal sequence CRLF CRLF becomes LF LF, not - LF. - -3.12.2. Examples - -3.12.2.1. Indented multi-line string - - multi-line """ - foo - This is the base indentation - bar - """ - - This example's string value will be: - - foo - This is the base indentation - bar - - which is equivalent to - - " foo\nThis is the base indentation\n bar" - - when written as a single-line string. - -3.12.2.2. Shorter last-line indent - - If the last line wasn't indented as far, it won't dedent the rest of - the lines as much: - - multi-line """ - foo - This is no longer on the left edge - bar - """ - - This example's string value will be: - - foo - This is no longer on the left edge - bar - - Equivalent to - - " foo\n This is no longer on the left edge\n bar" - -3.12.2.3. Empty lines - - Empty lines can contain any whitespace, or none at all, and will be - reflected as empty in the value: - - multi-line """ - Indented a bit - - A second indented paragraph. - """ - - This example's string value will be: - - Indented a bit. - - A second indented paragraph. - - Equivalent to - - "Indented a bit.\n\nA second indented paragraph." - -3.12.2.4. Syntax errors - - The following yield *syntax errors*: - - multi-line """can't be single line""" - - multi-line """ - closing quote with non-whitespace prefix""" - - multi-line """stuff - """ - - // Every line must share the exact same prefix as the closing line. - multi-line """[\n] - [tab]a[\n] - [space][space]b[\n] - [space][tab][\n] - [tab]""" - -3.12.3. Interaction with Whitespace Escapes - - Multi-line strings support the same mechanism for escaping whitespace - as Quoted Strings. - - When processing a Multi-line String, implementations MUST dedent the - string _after_ resolving all whitespace escapes, but _before_ - resolving other backslash escapes. This means a whitespace escape - that attempts to escape the final line's newline and/or whitespace - prefix can be invalid: if removing escaped whitespace places the - closing """ on a line with non-whitespace characters, this escape is - invalid. - - For example, the following example is illegal: - - """ - foo - bar\ - """ - - // equivalent to - """ - foo - bar""" - - while the following example is allowed - - """ - foo \ - bar - baz - \ """ - - // equivalent to - """ - foo bar - baz - """ - -3.13. Raw String - - Both Quoted (Section 3.11) and Multi-Line Strings (Section 3.12) have - Raw String variants, which are identical in syntax except they do not - support \-escapes. This includes line-continuation escapes (\ + ws - collapsing to nothing). They otherwise share the same properties as - far as literal Newline (Section 3.18) characters go, multi-line - rules, and the requirement of UTF-8 representation. - - The Raw String variants are indicated by preceding the strings's - opening quotes with one or more # characters. The string is then - closed by its normal closing quotes, followed by a _matching_ number - of # characters. This means that the string may contain any - combination of " and # characters other than its closing delimiter - (e.g., if a raw string starts with ##", it can contain " or "#, but - not "## or "###). - - Like other Strings, Raw Strings _MUST NOT_ include any of the - disallowed literal code-points (Section 3.19) as code points in their - body. Unlike with Quoted Strings, these cannot simply be escaped, - and are thus unrepresentable when using Raw Strings. - -3.13.1. Example - - just-escapes #"\n will be literal"# - - The string contains the literal characters \n will be literal. - - quotes-and-escapes ##"hello\n\r\asd"#world"## - - The string contains the literal characters hello\n\r\asd"#world - - raw-multi-line #""" - Here's a """ - multiline string - """ - without escapes. - """# - - The string contains the value - - Here's a """ - multiline string - """ - without escapes. - - or equivalently, - - "Here's a \"\"\"\n multiline string\n \"\"\"\nwithout escapes." - - as a Quoted String. - -3.14. Number - - Numbers in KDL represent numerical Values (Section 3.7). There is no - logical distinction in KDL between real numbers, integers, and - floating point numbers. It's up to individual implementations to - determine how to represent KDL numbers. - - There are five syntaxes for Numbers: Keywords, Decimal, Hexadecimal, - Octal, and Binary. - - * All non-Keyword (Section 3.14.1) numbers may optionally start with - one of - or +, which determine whether they'll be positive or - negative. - - * Binary numbers start with 0b and only allow 0 and 1 as digits, - which may be separated by _. They represent numbers in radix 2. - - * Octal numbers start with 0o and only allow digits between 0 and 7, - which may be separated by _. They represent numbers in radix 8. - - * Hexadecimal numbers start with 0x and allow digits between 0 and - 9, as well as letters A through F, in either lower or upper case, - which may be separated by _. They represent numbers in radix 16. - - * Decimal numbers are a bit more special: - - - They have no radix prefix. - - - They use digits 0 through 9, which may be separated by _. - - - They may optionally include a decimal separator ., followed by - more digits, which may again be separated by _. - - - They may optionally be followed by E or e, an optional - or +, - and more digits, to represent an exponent value. - - Note that, similar to JSON and some other languages, numbers without - an integer digit (such as .1) are illegal. They must be written with - at least one integer digit, like 0.1. (These patterns are also - disallowed from Identifier Strings (Section 3.10), to avoid - confusion.) - -3.14.1. Keyword Numbers - - There are three special "keyword" numbers included in KDL to - accomodate the widespread use of IEEE 754 - (https://en.wikipedia.org/wiki/IEEE_754) floats: - - * #inf - floating point positive infinity. - - * #-inf - floating point negative infinity. - - * #nan - floating point NaN/Not a Number. - - To go along with this and prevent foot guns, the bare Identifier - Strings (Section 3.10) inf, -inf, and nan are considered illegal - identifiers and should yield a syntax error. - - The existence of these keywords does not imply that any numbers be - represented as IEEE 754 floats. These are simply for clarity and - convenience for any implementation that chooses to represent their - numbers in this way. - -3.15. Boolean - - A boolean Value (Section 3.7) is either the symbol #true or #false. - These _SHOULD_ be represented by implementation as boolean logical - values, or some approximation thereof. - -3.15.1. Example - - my-node #true value=#false - -3.16. Null - - The symbol #null represents a null Value (Section 3.7). It's up to - the implementation to decide how to represent this, but it generally - signals the "absence" of a value. - -3.16.1. Example - - my-node #null key=#null - -3.17. Whitespace - - The following characters should be treated as non-Newline - (Section 3.18) white space - (https://www.unicode.org/Public/UCD/latest/ucd/PropList.txt): - - +===========================+=========+ - | Name | Code Pt | - +===========================+=========+ - | Character Tabulation | U+0009 | - +---------------------------+---------+ - | Space | U+0020 | - +---------------------------+---------+ - | No-Break Space | U+00A0 | - +---------------------------+---------+ - | Ogham Space Mark | U+1680 | - +---------------------------+---------+ - | En Quad | U+2000 | - +---------------------------+---------+ - | Em Quad | U+2001 | - +---------------------------+---------+ - | En Space | U+2002 | - +---------------------------+---------+ - | Em Space | U+2003 | - +---------------------------+---------+ - | Three-Per-Em Space | U+2004 | - +---------------------------+---------+ - | Four-Per-Em Space | U+2005 | - +---------------------------+---------+ - | Six-Per-Em Space | U+2006 | - +---------------------------+---------+ - | Figure Space | U+2007 | - +---------------------------+---------+ - | Punctuation Space | U+2008 | - +---------------------------+---------+ - | Thin Space | U+2009 | - +---------------------------+---------+ - | Hair Space | U+200A | - +---------------------------+---------+ - | Narrow No-Break Space | U+202F | - +---------------------------+---------+ - | Medium Mathematical Space | U+205F | - +---------------------------+---------+ - | Ideographic Space | U+3000 | - +---------------------------+---------+ - - Table 2 - -3.17.1. Single-line comments - - Any text after //, until the next literal Newline (Section 3.18) is - "commented out", and is considered to be Whitespace (Section 3.17). - -3.17.2. Multi-line comments - - In addition to single-line comments using //, comments can also be - started with /* and ended with */. These comments can span multiple - lines. They are allowed in all positions where Whitespace - (Section 3.17) is allowed and can be nested. - -3.17.3. Slashdash comments - - Finally, a special kind of comment called a "slashdash", denoted by - /-, can be used to comment out entire _components_ of a KDL document - logically, and have those elements not be included as part of the - parsed document data. - - Slashdash comments can be used before the following, including before - their type annotations, if present: - - * A Node (Section 3.2): the entire Node is treated as Whitespace, - including all props, args, and children. - - * An Argument (Section 3.5): the Argument value is treated as - Whitespace. - - * A Property (Section 3.4) key: the entire property, including both - key and value, is treated as Whitespace. A slashdash of just the - property value is not allowed. - - * A Children Block (Section 3.6): the entire block, including all - children within, is treated as Whitespace. Only other children - blocks, whether slashdashed or not, may follow a slashdashed - children block. - - A slashdash may be be followed by any amount of whitespace, including - newlines and comments (other than other slashdashes), before the - element that it comments out. - -3.18. Newline - - The following character sequences should be treated as new lines - (https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter- - 5/#G41643): - - +=========+===============================+=================+ - | Acronym | Name | Code Pt | - +=========+===============================+=================+ - | CRLF | Carriage Return and Line Feed | U+000D + U+000A | - +---------+-------------------------------+-----------------+ - | CR | Carriage Return | U+000D | - +---------+-------------------------------+-----------------+ - | LF | Line Feed | U+000A | - +---------+-------------------------------+-----------------+ - | NEL | Next Line | U+0085 | - +---------+-------------------------------+-----------------+ - | VT | Vertical tab | U+000B | - +---------+-------------------------------+-----------------+ - | FF | Form Feed | U+000C | - +---------+-------------------------------+-----------------+ - | LS | Line Separator | U+2028 | - +---------+-------------------------------+-----------------+ - | PS | Paragraph Separator | U+2029 | - +---------+-------------------------------+-----------------+ - - Table 3 - - Note that for the purpose of new lines, the specific sequence CRLF is - considered _a single newline_. - -3.19. Disallowed Literal Code Points - - The following code points may not appear literally anywhere in the - document. They may be represented in Strings (but not Raw Strings) - using Unicode Escapes (Section 3.11.1) (\u{...}, except for non - Unicode Scalar Value, which can't be represented even as escapes). - - * The codepoints U+0000-0008 or the codepoints U+000E-001F (various - control characters). - - * U+007F (the Delete control character). - - * Any codepoint that is not a Unicode Scalar Value - (https://unicode.org/glossary/#unicode_scalar_value) - (U+D800-DFFF). - - * U+200E-200F, U+202A-202E, and U+2066-2069, the unicode "direction - control" characters (https://www.w3.org/International/questions/ - qa-bidi-unicode-controls) - - * U+FEFF, aka Zero-width Non-breaking Space (ZWNBSP)/Byte Order Mark - (BOM), except as the first code point in a document. - -4. Full Grammar - - This is the full official grammar for KDL and should be considered - authoritative if something seems to disagree with the text above. - The grammar language syntax is defined in Section 4.1. - - document := bom? version? nodes - - // Nodes - nodes := (line-space* node)* line-space* - - base-node := slashdash? type? node-space* string - (node-space+ slashdash? node-prop-or-arg)* - // slashdashed node-children must always be after props and args. - (node-space+ slashdash node-children)* - (node-space+ node-children)? - (node-space+ slashdash node-children)* - node-space* - node := base-node node-terminator - final-node := base-node node-terminator? - - // Entries - node-prop-or-arg := prop | value - node-children := '{' nodes final-node? '}' - node-terminator := single-line-comment | newline | ';' | eof - - prop := string node-space* '=' node-space* value - value := type? node-space* (string | number | keyword) - type := '(' node-space* string node-space* ')' - - // Strings - string := identifier-string | quoted-string | raw-string ¶ - - identifier-string := unambiguous-ident | signed-ident | dotted-ident - unambiguous-ident := - ((identifier-char - digit - sign - '.') identifier-char*) - - disallowed-keyword-strings - signed-ident := - sign ((identifier-char - digit - '.') identifier-char*)? - dotted-ident := - sign? '.' ((identifier-char - digit) identifier-char*)? - identifier-char := - unicode - unicode-space - newline - [\\/(){};\[\]"#=] - - disallowed-literal-code-points - disallowed-keyword-identifiers := - 'true' | 'false' | 'null' | 'inf' | '-inf' | 'nan' - - quoted-string := - '"' single-line-string-body '"' | - '"""' newline - (multi-line-string-body newline)? - (unicode-space | ws-escape)* '"""' - single-line-string-body := (string-character - newline)* - multi-line-string-body := (('"' | '""')? string-character)* - string-character := - '\\' (["\\bfnrts] | - 'u{' hex-unicode '}') | - ws-escape | - [^\\"] - disallowed-literal-code-points - ws-escape := '\\' (unicode-space | newline)+ - hex-digit := [0-9a-fA-F] - hex-unicode := hex-digit{1, 6} - surrogate - above-max-scalar - surrogate := [0]{0, 2} [dD] [8-9a-fA-F] hex-digit{2} - // U+D800-DFFF: D 8 00 - // D F FF - above-max-scalar = [2-9a-fA-F] hex-digit{5} | - [1] [1-9a-fA-F] hex-digit{4} - - - raw-string := '#' raw-string-quotes '#' | '#' raw-string '#' - raw-string-quotes := - '"' single-line-raw-string-body '"' | - '"""' newline - (multi-line-raw-string-body newline)? - unicode-space* '"""' - single-line-raw-string-body := - '' | - (single-line-raw-string-char - '"') - single-line-raw-string-char*? | - '"' (single-line-raw-string-char - '"') - single-line-raw-string-char*? - single-line-raw-string-char := - unicode - newline - disallowed-literal-code-points - multi-line-raw-string-body := - (unicode - disallowed-literal-code-points)*? - - // Numbers - number := keyword-number | hex | octal | binary | decimal - - decimal := sign? integer ('.' integer)? exponent? - exponent := ('e' | 'E') sign? integer - integer := digit (digit | '_')* - digit := [0-9] - sign := '+' | '-' - - hex := sign? '0x' hex-digit (hex-digit | '_')* - octal := sign? '0o' [0-7] [0-7_]* - binary := sign? '0b' ('0' | '1') ('0' | '1' | '_')* - - // Keywords and booleans. - keyword := boolean | '#null' - keyword-number := '#inf' | '#-inf' | '#nan' - boolean := '#true' | '#false' - - // Specific code points - bom := '\u{FEFF}' - disallowed-literal-code-points := - See Table (Disallowed Literal Code Points) - unicode := Any Unicode Scalar Value - unicode-space := See Table - (All White_Space unicode characters which are not `newline`) - - // Comments - single-line-comment := '//' ^newline* (newline | eof) - multi-line-comment := '/*' commented-block - commented-block := - '*/' | (multi-line-comment | '*' | '/' | [^*/]+) commented-block - slashdash := '/-' line-space* - - // Whitespace - ws := unicode-space | multi-line-comment - escline := '\\' ws* (single-line-comment | newline | eof) - newline := See Table (All Newline White_Space) - // Whitespace where newlines are allowed. - line-space := node-space | newline | single-line-comment - // Whitespace within nodes, - // where newline-ish things must be esclined. - node-space := ws* escline ws* | ws+ - - // Version marker - version := - '/-' unicode-space* 'kdl-version' unicode-space+ ('1' | '2') - unicode-space* newline - -4.1. Grammar language - - The grammar language syntax is a combination of ABNF with some regex - spice thrown in. Specifically: - - * Single quotes (') are used to denote literal text. \ within a - literal string is used for escaping other single-quotes, for - initiating unicode characters using hex values (\u{FEFF}), and for - escaping \ itself (\\). - - * * is used for "zero or more", + is used for "one or more", and ? - is used for "zero or one". Per standard regex semantics, * and + - are _greedy_; they match as many instances as possible without - failing the match. - - * *? (used only in raw strings) indicates a _non-greedy_ match; it - matches as _few_ instances as possible without failing the match. - - * ¶ is a _cut point_. It always matches and consumes no characters, - but once matched, the parser is not allowed to backtrack past that - point in the source. If a parser would rewind past the cut point, - it must instead fail the overall parse, as if it had run out of - options. (This is only used with the raw-string production, to - ensure the first instance of the appropriate closing quote - sequence is guaranteed to be the end of the raw string, rather - than allowing it to potentially consume more of the document - unexpectedly.) - - * () can be used to group matches that must be matched together. - - * a | b means a or b, whichever matches first. If multiple items - are before a |, they are a single group. a b c | d is equivalent - to (a b c) | d. - - * [] are used for regex-style character matches, where any character - between the brackets will be a single match. \ is used to escape - \, [, and ]. They also support character ranges (0-9), and - negation (^) - - * - is used for "except for" or "minus" whatever follows it. For - example, a - 'x' means "any a, except something that matches the - literal 'x'". - - * The prefix ^ means "something that does not match" whatever - follows it. For example, ^foo means "must not match foo". - - * A single definition may be split over multiple lines. Newlines - are treated as spaces. - - * // followed by text on its own line is used as comment syntax. - -Authors' Addresses - - Katerina Zoé Marchán Salvá - Microsoft - - - The KDL Contributors diff --git a/zkat/fix-stuff/index.html b/zkat/fix-stuff/index.html deleted file mode 100644 index 6f93884..0000000 --- a/zkat/fix-stuff/index.html +++ /dev/null @@ -1,45 +0,0 @@ - - - - kdl-org/kdl zkat/fix-stuff preview - - - - -

Editor's drafts for zkat/fix-stuff branch of kdl-org/kdl

- - - - - - -
KDLplain textsame as main
- - - diff --git a/zkat/minor-tweaks/draft-marchan-kdl2.html b/zkat/minor-tweaks/draft-marchan-kdl2.html deleted file mode 100644 index c11a928..0000000 --- a/zkat/minor-tweaks/draft-marchan-kdl2.html +++ /dev/null @@ -1,2968 +0,0 @@ - - - - - - -The KDL Document Language - - - - - - - - - - - - - - - - - - - - - - - - - -
KDLJanuary 2025
Marchán & KDL ContributorsExperimental[Page]
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-
-
Workgroup:
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KDL Community
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Published:
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- -
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Authors:
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-
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K. Marchán
-
Microsoft
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KDL Contributors
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-
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-

The KDL Document Language

-
-

Abstract

-

KDL is a node-oriented document language. Its niche and purpose overlaps with -XML, and as do many of its semantics. You can use KDL both as a configuration -language, and a data exchange or storage format, if you so choose.

-

This is the formal specification for KDL, including the intended data model and -the grammar.

-

This document describes KDL version KDL 2.0.0. It was released on 2024-12-21. It -is the latest stable version of the language, and will only be edited for minor -copyedits or major errata.

-
-
-

-About This Document -

-

This note is to be removed before publishing as an RFC.

-

- Status information for this document may be found at https://datatracker.ietf.org/doc/draft-marchan-kdl2/.

-

- information can be found at https://kdl.dev/.

-

Source for this draft and an issue tracker can be found at - https://github.com/kdl-org/kdl.

-
-
-

-License -

-

This work is licensed under Creative Commons Attribution-ShareAlike 4.0 -International. To view a copy of this license, visit -https://creativecommons.org/licenses/by-sa/4.0/

-
-
-
- ▲

-Table of Contents -

- -
-
-
-
-

-1. Compatibility -

-

KDL 2.0 is designed such that for any given KDL document written as KDL -1.0 or KDL 2.0, the parse will either fail completely, or, if the -parse succeeds, the data represented by a v1 or v2 parser will be identical. -This means that it's safe to use a fallback parsing strategy in order to support -both v1 and v2 simultaneously. For example, node "foo" is a valid node in both -versions, and should be represented identically by parsers.

-

A version marker /- kdl-version 2 (or 1) MAY be added to the beginning of -a KDL document, optionally preceded by the BOM, and parsers MAY use that as a -hint as to which version to parse the document as.

-
-
-
-
-

-2. Introduction -

-

KDL is a node-oriented document language. Its niche and purpose overlaps with -XML, and as do many of its semantics. You can use KDL both as a configuration -language, and a data exchange or storage format, if you so choose.

-

The bulk of this document is dedicated to a long-form description of all -Components (Section 3) of a KDL document. -There is also a much more terse -Grammar (Section 4) at the end of the document that covers most of the -rules, with some semantic exceptions involving the data model.

-

KDL is designed to be easy to read and easy to implement.

-

In this document, references to "left" or "right" refer to directions in the -data stream towards the beginning or end, respectively; in other words, -the directions if the data stream were only ASCII text. They do not refer -to the writing direction of text, which can flow in either direction, -depending on the characters used.

-
-
-
-
-

-3. Components -

-
-
-

-3.1. Document -

-

The toplevel concept of KDL is a Document. A Document is composed of zero or -more Nodes (Section 3.2), separated by newlines and whitespace, and eventually -terminated by an EOF.

-

All KDL documents MUST be encoded in UTF-8 and conform to the specifications in -this document.

-
-
-

-3.1.1. Example -

-

The following is a document composed of two toplevel nodes:

-
-
-foo {
-    bar
-}
-baz
-
-
-
-
-
-
-
-
-

-3.2. Node -

-

Being a node-oriented language means that the real core component of any KDL -document is the "node". Every node must have a name, which must be a -String (Section 3.9).

-

The name may be preceded by a Type Annotation (Section 3.8) to further -clarify its type, particularly in relation to its parent node. (For example, -clarifying that a particular date child node is for the publication date, -rather than the last-modified date, with (published)date.)

-

Following the name are zero or more Arguments (Section 3.5) or -Properties (Section 3.4), separated by either whitespace (Section 3.17) or a -slash-escaped line continuation (Section 3.3). Arguments and Properties -may be interspersed in any order, much like is common with positional arguments -vs options in command line tools. Collectively, Arguments and Properties may be -referred to as "Entries".

-

Children (Section 3.6) can be placed after the name and the optional -Entries, possibly separated by either whitespace or a -slash-escaped line continuation.

-

Arguments are ordered relative to each other and that order must be preserved in -order to maintain the semantics. Properties between Arguments do not affect -Argument ordering.

-

By contrast, Properties SHOULD NOT be assumed to be presented in a given -order. Children (Section 3.6) should be used if an order-sensitive -key/value data structure must be represented in KDL. Cf. JSON objects -preserving key order.

-

Nodes MAY be prefixed with Slashdash (Section 3.17.3) to "comment out" -the entire node, including its properties, arguments, and children, and make -it act as plain whitespace, even if it spreads across multiple lines.

-

Finally, a node is terminated by either a Newline (Section 3.18), a semicolon -(;), the end of a child block (}) or the end of the file/stream (an EOF).

-
-
-

-3.2.1. Example -

-
-
-// `foo` will have an Argument value list like `[1, 3]`.
-foo 1 key=val 3 {
-    bar
-    (role)baz 1 2
-}
-
-
-
-
-
-
-
-
-

-3.3. Line Continuation -

-

Line continuations allow Nodes (Section 3.2) to be spread across multiple lines.

-

A line continuation is a \ character followed by zero or more whitespace -items (including multiline comments) and an optional single-line comment. It -must be terminated by a Newline (Section 3.18) (including the Newline that is -part of single-line comments).

-

Following a line continuation, processing of a Node can continue as usual.

-
-
-

-3.3.1. Example -

-
-
-my-node 1 2 \  // comments are ok after \
-        3 4    // This is the actual end of the Node.
-
-
-
-
-
-
-
-
-

-3.4. Property -

-

A Property is a key/value pair attached to a Node (Section 3.2). A Property is -composed of a String (Section 3.9), followed immediately by an equals sign (=, U+003D), -and then a Value (Section 3.7).

-

Properties should be interpreted left-to-right, with rightmost properties with -identical names overriding earlier properties. That is:

-
-
-node a=1 a=2
-
-
-

In this example, the node's a value must be 2, not 1.

-

No other guarantees about order should be expected by implementers. -Deserialized representations may iterate over properties in any order and -still be spec-compliant.

-

Properties MAY be prefixed with /- to "comment out" the entire token and -make it act as plain whitespace, even if it spreads across multiple lines.

-
-
-
-
-

-3.5. Argument -

-

An Argument is a bare Value (Section 3.7) attached to a Node (Section 3.2), with no -associated key. It shares the same space as Properties (Section 3.4), and may be interleaved with them.

-

A Node may have any number of Arguments, which should be evaluated left to -right. KDL implementations MUST preserve the order of Arguments relative to -each other (not counting Properties).

-

Arguments MAY be prefixed with /- to "comment out" the entire token and -make it act as plain whitespace, even if it spreads across multiple lines.

-
-
-

-3.5.1. Example -

-
-
-my-node 1 2 3 a b c
-
-
-
-
-
-
-
-
-

-3.6. Children Block -

-

A children block is a block of Nodes (Section 3.2), surrounded by { and }. They -are an optional part of nodes, and create a hierarchy of KDL nodes.

-

Regular node termination rules apply, which means multiple nodes can be -included in a single-line children block, as long as they're all terminated by -;.

-
-
-

-3.6.1. Example -

-
-
-parent {
-    child1
-    child2
-}
-
-parent { child1; child2; }
-
-
-
-
-
-
-
-
-

-3.7. Value -

-

A value is either: a String (Section 3.9), a Number (Section 3.14), a -Boolean (Section 3.15), or Null (Section 3.16).

-

Values MUST be either Arguments (Section 3.5) or values of -Properties (Section 3.4). Only String (Section 3.9) values may be used as -Node (Section 3.2) names or Property (Section 3.4) keys.

-

Values (both as arguments and in properties) MAY be prefixed by a single -Type Annotation (Section 3.8).

-
-
-
-
-

-3.8. Type Annotation -

-

A type annotation is a prefix to any Node Name (Section 3.2) or Value (Section 3.7) that -includes a suggestion of what type the value is intended to be treated as, -or as a context-specific elaboration of the more generic type the node name -indicates.

-

Type annotations are written as a set of ( and ) with a single -String (Section 3.9) in it. It may contain Whitespace after the ( and before -the ), and may be separated from its target by Whitespace.

-

KDL does not specify any restrictions on what implementations might do with -these annotations. They are free to ignore them, or use them to make decisions -about how to interpret a value.

-

Additionally, the following type annotations MAY be recognized by KDL parsers -and, if used, SHOULD interpret these types as follows:

-
-
-

-3.8.1. Reserved Type Annotations for Numbers Without Decimals: -

-

Signed integers of various sizes (the number is the bit size):

-
    -
  • -

    i8

    -
    • -
  • -

    i16

    -
    • -
  • -

    i32

    -
    • -
  • -

    i64

    -
    • -
  • -

    i128

    -
    • -
-

Unsigned integers of various sizes (the number is the bit size):

-
    -
  • -

    u8

    -
    • -
  • -

    u16

    -
    • -
  • -

    u32

    -
    • -
  • -

    u64

    -
    • -
  • -

    u128

    -
    • -
-

Platform-dependent integer types, both signed and unsigned:

-
    -
  • -

    isize

    -
    • -
  • -

    usize

    -
    • -
-
-
-
-
-

-3.8.2. Reserved Type Annotations for Numbers With Decimals: -

-

IEEE 754 floating point numbers, both single (32) and double (64) precision:

-
    -
  • -

    f32

    -
    • -
  • -

    f64

    -
    • -
-

IEEE 754-2008 decimal floating point numbers

-
    -
  • -

    decimal64

    -
    • -
  • -

    decimal128

    -
    • -
-
-
-
-
-

-3.8.3. Reserved Type Annotations for Strings: -

-
    -
  • -

    date-time: ISO8601 date/time format.

    -
    • -
  • -

    time: "Time" section of ISO8601.

    -
    • -
  • -

    date: "Date" section of ISO8601.

    -
    • -
  • -

    duration: ISO8601 duration format.

    -
    • -
  • -

    decimal: IEEE 754-2008 decimal string format.

    -
    • -
  • -

    currency: ISO 4217 currency code.

    -
    • -
  • -

    country-2: ISO 3166-1 alpha-2 country code.

    -
    • -
  • -

    country-3: ISO 3166-1 alpha-3 country code.

    -
    • -
  • -

    country-subdivision: ISO 3166-2 country subdivision code.

    -
    • -
  • -

    email: RFC5322 email address.

    -
    • -
  • -

    idn-email: RFC6531 internationalized email address.

    -
    • -
  • -

    hostname: RFC1123 internet hostname (only ASCII segments)

    -
    • -
  • -

    idn-hostname: RFC5890 internationalized internet hostname -(only xn---prefixed ASCII "punycode" segments, or non-ASCII segments)

    -
    • -
  • -

    ipv4: RFC2673 dotted-quad IPv4 address.

    -
    • -
  • -

    ipv6: RFC2373 IPv6 address.

    -
    • -
  • -

    url: RFC3986 URI.

    -
    • -
  • -

    url-reference: RFC3986 URI Reference.

    -
    • -
  • -

    irl: RFC3987 Internationalized Resource Identifier.

    -
    • -
  • -

    irl-reference: RFC3987 Internationalized Resource Identifier Reference.

    -
    • -
  • -

    url-template: RFC6570 URI Template.

    -
    • -
  • -

    uuid: RFC4122 UUID.

    -
    • -
  • -

    regex: Regular expression. Specific patterns may be implementation-dependent.

    -
    • -
  • -

    base64: A Base64-encoded string, denoting arbitrary binary data.

    -
    • -
-
-
-
-
-

-3.8.4. Examples -

-
-
-node (u8)123
-node prop=(regex).*
-(published)date "1970-01-01"
-(contributor)person name="Foo McBar"
-
-
-
-
-
-
-
-
-

-3.9. String -

-

Strings in KDL represent textual UTF-8 Values (Section 3.7). A String is either an -Identifier String (Section 3.10) (like foo), a -Quoted String (Section 3.11) (like "foo") -or a Multi-Line String (Section 3.12). -Both Quoted and Multiline strings come in normal -and Raw String (Section 3.13) variants (like #"foo"#):

-
    -
  • -

    Identifier Strings let you write short, "single-word" strings with a -minimum of syntax

    -
    • -
  • -

    Quoted Strings let you write strings "like normal", with whitespace and escapes.

    -
    • -
  • -

    Multi-Line Strings let you write strings across multiple lines - and with indentation that's not part of the string value.

    -
    • -
  • -

    Raw Strings don't allow any escapes, -allowing you to not worry about the string's content containing anything that -might look like an escape.

    -
    • -
-

Strings MUST be represented as UTF-8 values.

-

Strings MUST NOT include the code points for -disallowed literal code points (Section 3.19) directly. -Quoted and Multi-Line Strings may include these code points as values -by representing them with their corresponding \u{...} escape.

-
-
-
-
-

-3.10. Identifier String -

-

An Identifier String (sometimes referred to as just an "identifier") is -composed of any Unicode Scalar -Value other than -non-initial characters (Section 3.10.1), followed by any number of -Unicode Scalar Values other than non-identifier -characters (Section 3.10.2).

-

A handful of patterns are disallowed, to avoid confusion with other values:

-
    -
  • -

    idents that appear to start with a Number (Section 3.14) (like 1.0v2 or - -1em) or the "almost a number" pattern of a decimal point without a - leading digit (like .1).

    -
    • -
  • -

    idents that are the language keywords (inf, -inf, nan, true, -false, and null) without their leading #.

    -
    • -
-

Identifiers that match these patterns MUST be treated as a syntax error; such -values can only be written as quoted or raw strings. The precise details of the -identifier syntax is specified in the Full Grammar in Section 4.

-
-
-

-3.10.1. Non-initial characters -

-

The following characters cannot be the first character in an -Identifier String (Section 3.10):

-
    -
  • -

    Any decimal digit (0-9)

    -
    • -
  • -

    Any non-identifier characters (Section 3.10.2)

    -
    • -
-

Additionally, the following initial characters impose limitations on subsequent -characters:

-
    -
  • -

    the + and - characters can only be used as an initial character if -the second character is not a digit. If the second character is ., then -the third character must not be a digit.

    -
    • -
  • -

    the . character can only be used as an initial character if -the second character is not a digit.

    -
    • -
-

This allows identifiers to look like --this or .md, and removes the -ambiguity of having an identifier look like a number.

-
-
-
-
-

-3.10.2. Non-identifier characters -

-

The following characters cannot be used anywhere in a Identifier String (Section 3.10):

- -
-
-
-
-
-
-

-3.11. Quoted String -

-

A Quoted String is delimited by " on either side of any number of literal -string characters except unescaped " and \.

-

Literal Newline (Section 3.18) characters can only be included -if they are Escaped Whitespace (Section 3.11.1.1), -which discards them from the string value. -Actually including a newline in the value requires using a newline escape sequence, -like \n, -or using a Multi-Line String (Section 3.12) -which is actually designed for strings stretching across multiple lines.

-

Like Identifier Strings, Quoted Strings MUST NOT include any of the -disallowed literal code-points (Section 3.19) as code -points in their body.

-

Quoted Strings have a Raw String (Section 3.13) variant, -which disallows escapes.

-
-
-

-3.11.1. Escapes -

-

In addition to literal code points, a number of "escapes" are supported in Quoted Strings. -"Escapes" are the character \ followed by another character, and are -interpreted as described in the following table:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table 1
NameEscapeCode Pt
Line Feed - \n - - U+000A -
Carriage Return - \r - - U+000D -
Character Tabulation (Tab) - \t - - U+0009 -
Reverse Solidus (Backslash) - \\ - - U+005C -
Quotation Mark (Double Quote) - \" - - U+0022 -
Backspace - \b - - U+0008 -
Form Feed - \f - - U+000C -
Space - \s - - U+0020 -
Unicode Escape - \u{(1-6 hex chars)} -Code point described by hex characters, as long as it represents a Unicode Scalar Value -
Whitespace EscapeSee belowN/A
-
-
-
-3.11.1.1. Escaped Whitespace -
-

In addition to escaping individual characters, \ can also escape whitespace. -When a \ is followed by one or more literal whitespace characters, the \ -and all of that whitespace are discarded. For example,

-
-
-"Hello World"
-
-
-

and

-
-
-"Hello \    World"
-
-
-

are semantically identical. See whitespace (Section 3.17) -and newlines (Section 3.18) for how whitespace is defined.

-

Note that only literal whitespace is escaped; whitespace escapes (\n and -such) are retained. For example, these strings are all semantically identical:

-
-
-"Hello\       \nWorld"
-
-    "Hello\n\
-    World"
-
-"Hello\nWorld"
-
-"""
-  Hello
-  World
-  """
-
-
-
-
-
-
-
-3.11.1.2. Invalid escapes -
-

Except as described in the escapes table, above, \ MUST NOT precede any -other characters in a string.

-
-
-
-
-
-
-
-
-

-3.12. Multi-line String -

-

Multi-Line Strings support multiple lines with literal, non-escaped -Newlines. They must use a special multi-line syntax, and they automatically -"dedent" the string, allowing its value to be indented to a visually matching -level as desired.

-

A Multi-Line String is opened and closed by three double-quote characters, -like """. -Its first line MUST immediately start with a Newline (Section 3.18) -after its opening """. -Its final line MUST contain only whitespace -before the closing """. -All in-between lines that contain non-newline, non-whitespace characters -MUST start with at least the exact same whitespace as the final line -(precisely matching codepoints, not merely counting characters or "size"); -they may contain additional whitespace following this prefix. The lines in -between may contain unescaped " (but no unescaped """ as this would close -the string).

-

The value of the Multi-Line String omits the first and last Newline, the -Whitespace of the last line, and the matching Whitespace prefix on all -intermediate lines. The first and last Newline can be the same character (that -is, empty multi-line strings are legal).

-

In other words, the final line specifies the whitespace prefix that will be -removed from all other lines.

-

Multi-line Strings that do not immediately start with a Newline and whose final -""" is not preceeded by optional whitespace and a Newline are illegal. This -also means that """ may not be used for a single-line String (e.g. -"""foo""").

-
-
-

-3.12.1. Newline Normalization -

-

Literal Newline sequences in Multi-line Strings must be normalized to a single -U+000A (LF) during deserialization. This means, for example, that CR LF -becomes a single LF during parsing.

-

This normalization does not apply to non-literal Newlines entered using escape -sequences. That is:

-
-
-multi-line """
-    \r\n[CRLF]
-    foo[CRLF]
-    """
-
-
-

becomes:

-
-
-single-line "\r\n\nfoo"
-
-
-

For clarity: this normalization applies to each individual Newline sequence. -That is, the literal sequence CRLF CRLF becomes LF LF, not LF.

-
-
-
-
-

-3.12.2. Examples -

-
-
-
-3.12.2.1. Indented multi-line string -
-
-
-multi-line """
-        foo
-    This is the base indentation
-            bar
-    """
-
-
-

This example's string value will be:

-
-
-    foo
-This is the base indentation
-        bar
-
-
-

which is equivalent to

-
-
-"    foo\nThis is the base indentation\n        bar"
-
-
-

when written as a single-line string.

-
-
-
-
-
-3.12.2.2. Shorter last-line indent -
-

If the last line wasn't indented as far, -it won't dedent the rest of the lines as much:

-
-
-multi-line """
-        foo
-    This is no longer on the left edge
-            bar
-  """
-
-
-

This example's string value will be:

-
-
-      foo
-  This is no longer on the left edge
-          bar
-
-
-

Equivalent to

-
-
-"      foo\n  This is no longer on the left edge\n          bar"
-
-
-
-
-
-
-
-3.12.2.3. Empty lines -
-

Empty lines can contain any whitespace, or none at all, and will be reflected as empty in the value:

-
-
-multi-line """
-    Indented a bit
-
-    A second indented paragraph.
-    """
-
-
-

This example's string value will be:

-
-
-Indented a bit.
-
-A second indented paragraph.
-
-
-

Equivalent to

-
-
-"Indented a bit.\n\nA second indented paragraph."
-
-
-
-
-
-
-
-3.12.2.4. Syntax errors -
-

The following yield syntax errors:

-
-
-multi-line """can't be single line"""
-
-
-
-
-multi-line """
-  closing quote with non-whitespace prefix"""
-
-
-
-
-multi-line """stuff
-  """
-
-
-
-
-// Every line must share the exact same prefix as the closing line.
-multi-line """[\n]
-[tab]a[\n]
-[space][space]b[\n]
-[space][tab][\n]
-[tab]"""
-
-
-
-
-
-
-
-
-

-3.12.3. Interaction with Whitespace Escapes -

-

Multi-line strings support the same mechanism for escaping whitespace as Quoted -Strings.

-

When processing a Multi-line String, implementations MUST dedent the string -after resolving all whitespace escapes, but before resolving other backslash -escapes. This means a whitespace escape that attempts to escape the final line's -newline and/or whitespace prefix can be invalid: if removing escaped whitespace -places the closing """ on a line with non-whitespace characters, this escape -is invalid.

-

For example, the following example is illegal:

-
-
-  """
-  foo
-  bar\
-  """
-
-  // equivalent to
-  """
-  foo
-  bar"""
-
-
-

while the following example is allowed

-
-
-  """
-  foo \
-bar
-  baz
-  \   """
-
-  // equivalent to
-  """
-  foo bar
-  baz
-  """
-
-
-
-
-
-
-
-
-

-3.13. Raw String -

-

Both Quoted (Section 3.11) and Multi-Line Strings (Section 3.12) have -Raw String variants, which are identical in syntax except they do not support -\-escapes. This includes line-continuation escapes (\ + ws collapsing to -nothing). They otherwise share the same properties as far as literal -Newline (Section 3.18) characters go, multi-line rules, and the requirement of -UTF-8 representation.

-

The Raw String variants are indicated by preceding the strings's opening quotes -with one or more # characters. The string is then closed by its normal closing -quotes, followed by a matching number of # characters. This means that the -string may contain any combination of " and # characters other than its -closing delimiter (e.g., if a raw string starts with ##", it can contain " -or "#, but not "## or "###).

-

Like other Strings, Raw Strings MUST NOT include any of the disallowed -literal code-points (Section 3.19) as code points in their -body. Unlike with Quoted Strings, these cannot simply be escaped, and are thus -unrepresentable when using Raw Strings.

-
-
-

-3.13.1. Example -

-
-
-just-escapes #"\n will be literal"#
-
-
-

The string contains the literal characters \n will be literal.

-
-
-quotes-and-escapes ##"hello\n\r\asd"#world"##
-
-
-

The string contains the literal characters hello\n\r\asd"#world

-
-
-raw-multi-line #"""
-    Here's a """
-        multiline string
-        """
-    without escapes.
-    """#
-
-
-

The string contains the value

-
-
-Here's a """
-    multiline string
-    """
-without escapes.
-
-
-

or equivalently,

-
-
-"Here's a \"\"\"\n    multiline string\n    \"\"\"\nwithout escapes."
-
-
-

as a Quoted String.

-
-
-
-
-
-
-

-3.14. Number -

-

Numbers in KDL represent numerical Values (Section 3.7). There is no logical distinction in KDL -between real numbers, integers, and floating point numbers. It's up to -individual implementations to determine how to represent KDL numbers.

-

There are five syntaxes for Numbers: Keywords, Decimal, Hexadecimal, Octal, and Binary.

-
    -
  • -

    All non-Keyword (Section 3.14.1) numbers may optionally start with one of - or +, which determine whether they'll be positive or negative.

    -
    • -
  • -

    Binary numbers start with 0b and only allow 0 and 1 as digits, which may be separated by _. They represent numbers in radix 2.

    -
    • -
  • -

    Octal numbers start with 0o and only allow digits between 0 and 7, which may be separated by _. They represent numbers in radix 8.

    -
    • -
  • -

    Hexadecimal numbers start with 0x and allow digits between 0 and 9, as well as letters A through F, in either lower or upper case, which may be separated by _. They represent numbers in radix 16.

    -
    • -
  • -

    Decimal numbers are a bit more special:

    -
      -
    • -

      They have no radix prefix.

      -
      • -
    • -

      They use digits 0 through 9, which may be separated by _.

      -
      • -
    • -

      They may optionally include a decimal separator ., followed by more digits, which may again be separated by _.

      -
      • -
    • -

      They may optionally be followed by E or e, an optional - or +, and more digits, to represent an exponent value.

      -
      • -
    -
    • -
-

Note that, similar to JSON and some other languages, -numbers without an integer digit (such as .1) are illegal. -They must be written with at least one integer digit, like 0.1. -(These patterns are also disallowed from Identifier Strings (Section 3.10), to avoid confusion.)

-
-
-

-3.14.1. Keyword Numbers -

-

There are three special "keyword" numbers included in KDL to accomodate the -widespread use of IEEE 754 floats:

-
    -
  • -

    #inf - floating point positive infinity.

    -
    • -
  • -

    #-inf - floating point negative infinity.

    -
    • -
  • -

    #nan - floating point NaN/Not a Number.

    -
    • -
-

To go along with this and prevent foot guns, the bare Identifier -Strings (Section 3.10) inf, -inf, and nan are considered illegal -identifiers and should yield a syntax error.

-

The existence of these keywords does not imply that any numbers be represented -as IEEE 754 floats. These are simply for clarity and convenience for any -implementation that chooses to represent their numbers in this way.

-
-
-
-
-
-
-

-3.15. Boolean -

-

A boolean Value (Section 3.7) is either the symbol #true or #false. These -SHOULD be represented by implementation as boolean logical values, or some -approximation thereof.

-
-
-

-3.15.1. Example -

-
-
-my-node #true value=#false
-
-
-
-
-
-
-
-
-

-3.16. Null -

-

The symbol #null represents a null Value (Section 3.7). It's up to the -implementation to decide how to represent this, but it generally signals the -"absence" of a value.

-
-
-

-3.16.1. Example -

-
-
-my-node #null key=#null
-
-
-
-
-
-
-
-
-

-3.17. Whitespace -

-

The following characters should be treated as non-Newline (Section 3.18) white -space:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table 2
NameCode Pt
Character Tabulation - U+0009 -
Space - U+0020 -
No-Break Space - U+00A0 -
Ogham Space Mark - U+1680 -
En Quad - U+2000 -
Em Quad - U+2001 -
En Space - U+2002 -
Em Space - U+2003 -
Three-Per-Em Space - U+2004 -
Four-Per-Em Space - U+2005 -
Six-Per-Em Space - U+2006 -
Figure Space - U+2007 -
Punctuation Space - U+2008 -
Thin Space - U+2009 -
Hair Space - U+200A -
Narrow No-Break Space - U+202F -
Medium Mathematical Space - U+205F -
Ideographic Space - U+3000 -
-
-
-

-3.17.1. Single-line comments -

-

Any text after //, until the next literal Newline (Section 3.18) is "commented -out", and is considered to be Whitespace (Section 3.17).

-
-
-
-
-

-3.17.2. Multi-line comments -

-

In addition to single-line comments using //, comments can also be started -with /* and ended with */. These comments can span multiple lines. They -are allowed in all positions where Whitespace (Section 3.17) is allowed and -can be nested.

-
-
-
-
-

-3.17.3. Slashdash comments -

-

Finally, a special kind of comment called a "slashdash", denoted by /-, can -be used to comment out entire components of a KDL document logically, and -have those elements not be included as part of the parsed document data.

-

Slashdash comments can be used before the following, including before their type -annotations, if present:

-
    -
  • -

    A Node (Section 3.2): the entire Node is treated as Whitespace, including all -props, args, and children.

    -
    • -
  • -

    An Argument (Section 3.5): the Argument value is treated as Whitespace.

    -
    • -
  • -

    A Property (Section 3.4) key: the entire property, including both key and value, -is treated as Whitespace. A slashdash of just the property value is not allowed.

    -
    • -
  • -

    A Children Block (Section 3.6): the entire block, including all -children within, is treated as Whitespace. Only other children blocks, whether -slashdashed or not, may follow a slashdashed children block.

    -
    • -
-

A slashdash may be be followed by any amount of whitespace, including newlines and -comments (other than other slashdashes), before the element that it comments out.

-
-
-
-
-
-
-

-3.18. Newline -

-

The following character sequences should be treated as new -lines:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table 3
AcronymNameCode Pt
CRLFCarriage Return and Line Feed - U+000D + U+000A -
CRCarriage Return - U+000D -
LFLine Feed - U+000A -
NELNext Line - U+0085 -
VTVertical tab - U+000B -
FFForm Feed - U+000C -
LSLine Separator - U+2028 -
PSParagraph Separator - U+2029 -
-

Note that for the purpose of new lines, the specific sequence CRLF is -considered a single newline.

-
-
-
-
-

-3.19. Disallowed Literal Code Points -

-

The following code points may not appear literally anywhere in the document. -They may be represented in Strings (but not Raw Strings) using Unicode Escapes (Section 3.11.1) (\u{...}, -except for non Unicode Scalar Value, which can't be represented even as escapes).

-
    -
  • -

    The codepoints U+0000-0008 or the codepoints U+000E-001F (various -control characters).

    -
    • -
  • -

    U+007F (the Delete control character).

    -
    • -
  • -

    Any codepoint that is not a Unicode Scalar -Value (U+D800-DFFF).

    -
    • -
  • -

    U+200E-200F, U+202A-202E, and U+2066-2069, the unicode -"direction control" -characters

    -
    • -
  • -

    U+FEFF, aka Zero-width Non-breaking Space (ZWNBSP)/Byte Order Mark (BOM), -except as the first code point in a document.

    -
    • -
-
-
-
-
-
-
-

-4. Full Grammar -

-

This is the full official grammar for KDL and should be considered -authoritative if something seems to disagree with the text above. The grammar -language syntax is defined in Section 4.1.

-
-
-document := bom? version? nodes
-
-// Nodes
-nodes := (line-space* node)* line-space*
-
-base-node := slashdash? type? node-space* string
-    (node-space+ slashdash? node-prop-or-arg)*
-    // slashdashed node-children must always be after props and args.
-    (node-space+ slashdash node-children)*
-    (node-space+ node-children)?
-    (node-space+ slashdash node-children)*
-    node-space*
-node := base-node node-terminator
-final-node := base-node node-terminator?
-
-// Entries
-node-prop-or-arg := prop | value
-node-children := '{' nodes final-node? '}'
-node-terminator := single-line-comment | newline | ';' | eof
-
-prop := string node-space* '=' node-space* value
-value := type? node-space* (string | number | keyword)
-type := '(' node-space* string node-space* ')'
-
-// Strings
-string := identifier-string | quoted-string | raw-string ¶
-
-identifier-string := unambiguous-ident | signed-ident | dotted-ident
-unambiguous-ident :=
-    ((identifier-char - digit - sign - '.') identifier-char*)
-    - disallowed-keyword-strings
-signed-ident :=
-    sign ((identifier-char - digit - '.') identifier-char*)?
-dotted-ident :=
-    sign? '.' ((identifier-char - digit) identifier-char*)?
-identifier-char :=
-    unicode - unicode-space - newline - [\\/(){};\[\]"#=]
-    - disallowed-literal-code-points
-disallowed-keyword-identifiers :=
-    'true' | 'false' | 'null' | 'inf' | '-inf' | 'nan'
-
-quoted-string :=
-    '"' single-line-string-body '"' |
-    '"""' newline
-    (multi-line-string-body newline)?
-    (unicode-space | ws-escape)* '"""'
-single-line-string-body := (string-character - newline)*
-multi-line-string-body := (('"' | '""')? string-character)*
-string-character :=
-    '\\' (["\\bfnrts] |
-    'u{' hex-unicode '}') |
-    ws-escape |
-    [^\\"] - disallowed-literal-code-points
-ws-escape := '\\' (unicode-space | newline)+
-hex-digit := [0-9a-fA-F]
-hex-unicode := hex-digit{1, 6} - surrogate - above-max-scalar  // Unicode Scalar Value in hex₁₆, leading 0s allowed within length ≤ 6
-surrogate := [0]{0, 2} [dD] [8-9a-fA-F] hex-digit{2}
-//  U+D800-DFFF:         D   8          00
-//                       D   F          FF
-above-max-scalar = [2-9a-fA-F] hex-digit{5} | [1] [1-9a-fA-F] hex-digit{4}
-// >U+10FFFF:      >1          _____           1  >0          ____
-
-
-raw-string := '#' raw-string-quotes '#' | '#' raw-string '#'
-raw-string-quotes :=
-    '"' single-line-raw-string-body '"' |
-    '"""' newline
-    (multi-line-raw-string-body newline)?
-    unicode-space* '"""'
-single-line-raw-string-body :=
-    '' |
-    (single-line-raw-string-char - '"')
-        single-line-raw-string-char*? |
-    '"' (single-line-raw-string-char - '"')
-        single-line-raw-string-char*?
-single-line-raw-string-char :=
-    unicode - newline - disallowed-literal-code-points
-multi-line-raw-string-body :=
-    (unicode - disallowed-literal-code-points)*?
-
-// Numbers
-number := keyword-number | hex | octal | binary | decimal
-
-decimal := sign? integer ('.' integer)? exponent?
-exponent := ('e' | 'E') sign? integer
-integer := digit (digit | '_')*
-digit := [0-9]
-sign := '+' | '-'
-
-hex := sign? '0x' hex-digit (hex-digit | '_')*
-octal := sign? '0o' [0-7] [0-7_]*
-binary := sign? '0b' ('0' | '1') ('0' | '1' | '_')*
-
-// Keywords and booleans.
-keyword := boolean | '#null'
-keyword-number := '#inf' | '#-inf' | '#nan'
-boolean := '#true' | '#false'
-
-// Specific code points
-bom := '\u{FEFF}'
-disallowed-literal-code-points :=
-    See Table (Disallowed Literal Code Points)
-unicode := Any Unicode Scalar Value
-unicode-space := See Table
-    (All White_Space unicode characters which are not `newline`)
-
-// Comments
-single-line-comment := '//' ^newline* (newline | eof)
-multi-line-comment := '/*' commented-block
-commented-block :=
-    '*/' | (multi-line-comment | '*' | '/' | [^*/]+) commented-block
-slashdash := '/-' line-space*
-
-// Whitespace
-ws := unicode-space | multi-line-comment
-escline := '\\' ws* (single-line-comment | newline | eof)
-newline := See Table (All Newline White_Space)
-// Whitespace where newlines are allowed.
-line-space := node-space | newline | single-line-comment
-// Whitespace within nodes,
-// where newline-ish things must be esclined.
-node-space := ws* escline ws* | ws+
-
-// Version marker
-version :=
-    '/-' unicode-space* 'kdl-version' unicode-space+ ('1' | '2')
-    unicode-space* newline
-
-
-
-
-

-4.1. Grammar language -

-

The grammar language syntax is a combination of ABNF with some regex spice thrown in. -Specifically:

-
    -
  • -

    Single quotes (') are used to denote literal text. \ within a literal -string is used for escaping other single-quotes, for initiating unicode -characters using hex values (\u{FEFF}), and for escaping \ itself -(\\).

    -
    • -
  • -

    * is used for "zero or more", + is used for "one or more", and ? is -used for "zero or one". Per standard regex semantics, * and + are greedy; -they match as many instances as possible without failing the match.

    -
    • -
  • -

    *? (used only in raw strings) indicates a non-greedy match; -it matches as few instances as possible without failing the match.

    -
    • -
  • -

    is a cut point. It always matches and consumes no characters, -but once matched, the parser is not allowed to backtrack past that point in the source. -If a parser would rewind past the cut point, it must instead fail the overall parse, -as if it had run out of options. -(This is only used with the raw-string production, -to ensure the first instance of the appropriate closing quote sequence -is guaranteed to be the end of the raw string, -rather than allowing it to potentially consume more of the document unexpectedly.)

    -
    • -
  • -

    () can be used to group matches that must be matched together.

    -
    • -
  • -

    a | b means a or b, whichever matches first. If multiple items are before -a |, they are a single group. a b c | d is equivalent to (a b c) | d.

    -
    • -
  • -

    [] are used for regex-style character matches, where any character between -the brackets will be a single match. \ is used to escape \, [, and -]. They also support character ranges (0-9), and negation (^)

    -
    • -
  • -

    - is used for "except for" or "minus" whatever follows it. For example, -a - 'x' means "any a, except something that matches the literal 'x'".

    -
    • -
  • -

    The prefix ^ means "something that does not match" whatever follows it. -For example, ^foo means "must not match foo".

    -
    • -
  • -

    A single definition may be split over multiple lines. Newlines are treated as -spaces.

    -
    • -
  • -

    // followed by text on its own line is used as comment syntax.

    -
    • -
-
-
-
-
-
-
-

-Authors' Addresses -

-
-
Katerina Zoé Marchán Salvá
-
Microsoft
-
-
-
The KDL Contributors
-
-
-
- - - diff --git a/zkat/minor-tweaks/draft-marchan-kdl2.txt b/zkat/minor-tweaks/draft-marchan-kdl2.txt deleted file mode 100644 index b0d7ff6..0000000 --- a/zkat/minor-tweaks/draft-marchan-kdl2.txt +++ /dev/null @@ -1,1244 +0,0 @@ - - - - -KDL Community K. Marchán - Microsoft - KDL Contributors - 23 January 2025 - - - The KDL Document Language - draft-marchan-kdl2-latest - -Abstract - - KDL is a node-oriented document language. Its niche and purpose - overlaps with XML, and as do many of its semantics. You can use KDL - both as a configuration language, and a data exchange or storage - format, if you so choose. - - This is the formal specification for KDL, including the intended data - model and the grammar. - - This document describes KDL version KDL 2.0.0. It was released on - 2024-12-21. It is the latest stable version of the language, and - will only be edited for minor copyedits or major errata. - -About This Document - - This note is to be removed before publishing as an RFC. - - Status information for this document may be found at - https://datatracker.ietf.org/doc/draft-marchan-kdl2/. - - information can be found at https://kdl.dev/. - - Source for this draft and an issue tracker can be found at - https://github.com/kdl-org/kdl. - -License - - This work is licensed under Creative Commons Attribution-ShareAlike - 4.0 International. To view a copy of this license, visit - https://creativecommons.org/licenses/by-sa/4.0/ - -Table of Contents - - 1. Compatibility - 2. Introduction - 3. Components - 3.1. Document - 3.1.1. Example - 3.2. Node - 3.2.1. Example - 3.3. Line Continuation - 3.3.1. Example - 3.4. Property - 3.5. Argument - 3.5.1. Example - 3.6. Children Block - 3.6.1. Example - 3.7. Value - 3.8. Type Annotation - 3.8.1. Reserved Type Annotations for Numbers Without Decimals: - 3.8.2. Reserved Type Annotations for Numbers With Decimals: - 3.8.3. Reserved Type Annotations for Strings: - 3.8.4. Examples - 3.9. String - 3.10. Identifier String - 3.10.1. Non-initial characters - 3.10.2. Non-identifier characters - 3.11. Quoted String - 3.11.1. Escapes - 3.12. Multi-line String - 3.12.1. Newline Normalization - 3.12.2. Examples - 3.12.3. Interaction with Whitespace Escapes - 3.13. Raw String - 3.13.1. Example - 3.14. Number - 3.14.1. Keyword Numbers - 3.15. Boolean - 3.15.1. Example - 3.16. Null - 3.16.1. Example - 3.17. Whitespace - 3.17.1. Single-line comments - 3.17.2. Multi-line comments - 3.17.3. Slashdash comments - 3.18. Newline - 3.19. Disallowed Literal Code Points - 4. Full Grammar - 4.1. Grammar language - Authors' Addresses - -1. Compatibility - - KDL 2.0 is designed such that for any given KDL document written as - KDL 1.0 (./SPEC_v1.md) or KDL 2.0, the parse will either fail - completely, or, if the parse succeeds, the data represented by a v1 - or v2 parser will be identical. This means that it's safe to use a - fallback parsing strategy in order to support both v1 and v2 - simultaneously. For example, node "foo" is a valid node in both - versions, and should be represented identically by parsers. - - A version marker /- kdl-version 2 (or 1) _MAY_ be added to the - beginning of a KDL document, optionally preceded by the BOM, and - parsers _MAY_ use that as a hint as to which version to parse the - document as. - -2. Introduction - - KDL is a node-oriented document language. Its niche and purpose - overlaps with XML, and as do many of its semantics. You can use KDL - both as a configuration language, and a data exchange or storage - format, if you so choose. - - The bulk of this document is dedicated to a long-form description of - all Components (Section 3) of a KDL document. There is also a much - more terse Grammar (Section 4) at the end of the document that covers - most of the rules, with some semantic exceptions involving the data - model. - - KDL is designed to be easy to read _and_ easy to implement. - - In this document, references to "left" or "right" refer to directions - in the _data stream_ towards the beginning or end, respectively; in - other words, the directions if the data stream were only ASCII text. - They do not refer to the writing direction of text, which can flow in - either direction, depending on the characters used. - -3. Components - -3.1. Document - - The toplevel concept of KDL is a Document. A Document is composed of - zero or more Nodes (Section 3.2), separated by newlines and - whitespace, and eventually terminated by an EOF. - - All KDL documents MUST be encoded in UTF-8 and conform to the - specifications in this document. - -3.1.1. Example - - The following is a document composed of two toplevel nodes: - - foo { - bar - } - baz - -3.2. Node - - Being a node-oriented language means that the real core component of - any KDL document is the "node". Every node must have a name, which - must be a String (Section 3.9). - - The name may be preceded by a Type Annotation (Section 3.8) to - further clarify its type, particularly in relation to its parent - node. (For example, clarifying that a particular date child node is - for the _publication_ date, rather than the last-modified date, with - (published)date.) - - Following the name are zero or more Arguments (Section 3.5) or - Properties (Section 3.4), separated by either whitespace - (Section 3.17) or a slash-escaped line continuation (Section 3.3). - Arguments and Properties may be interspersed in any order, much like - is common with positional arguments vs options in command line tools. - Collectively, Arguments and Properties may be referred to as - "Entries". - - Children (Section 3.6) can be placed after the name and the optional - Entries, possibly separated by either whitespace or a slash-escaped - line continuation. - - Arguments are ordered relative to each other and that order must be - preserved in order to maintain the semantics. Properties between - Arguments do not affect Argument ordering. - - By contrast, Properties _SHOULD NOT_ be assumed to be presented in a - given order. Children (Section 3.6) should be used if an order- - sensitive key/value data structure must be represented in KDL. Cf. - JSON objects preserving key order. - - Nodes _MAY_ be prefixed with Slashdash (Section 3.17.3) to "comment - out" the entire node, including its properties, arguments, and - children, and make it act as plain whitespace, even if it spreads - across multiple lines. - - Finally, a node is terminated by either a Newline (Section 3.18), a - semicolon (;), the end of a child block (}) or the end of the file/ - stream (an EOF). - -3.2.1. Example - - // `foo` will have an Argument value list like `[1, 3]`. - foo 1 key=val 3 { - bar - (role)baz 1 2 - } - -3.3. Line Continuation - - Line continuations allow Nodes (Section 3.2) to be spread across - multiple lines. - - A line continuation is a \ character followed by zero or more - whitespace items (including multiline comments) and an optional - single-line comment. It must be terminated by a Newline - (Section 3.18) (including the Newline that is part of single-line - comments). - - Following a line continuation, processing of a Node can continue as - usual. - -3.3.1. Example - - my-node 1 2 \ // comments are ok after \ - 3 4 // This is the actual end of the Node. - -3.4. Property - - A Property is a key/value pair attached to a Node (Section 3.2). A - Property is composed of a String (Section 3.9), followed immediately - by an equals sign (=, U+003D), and then a Value (Section 3.7). - - Properties should be interpreted left-to-right, with rightmost - properties with identical names overriding earlier properties. That - is: - - node a=1 a=2 - - In this example, the node's a value must be 2, not 1. - - No other guarantees about order should be expected by implementers. - Deserialized representations may iterate over properties in any order - and still be spec-compliant. - - Properties _MAY_ be prefixed with /- to "comment out" the entire - token and make it act as plain whitespace, even if it spreads across - multiple lines. - -3.5. Argument - - An Argument is a bare Value (Section 3.7) attached to a Node - (Section 3.2), with no associated key. It shares the same space as - Properties (Section 3.4), and may be interleaved with them. - - A Node may have any number of Arguments, which should be evaluated - left to right. KDL implementations _MUST_ preserve the order of - Arguments relative to each other (not counting Properties). - - Arguments _MAY_ be prefixed with /- to "comment out" the entire token - and make it act as plain whitespace, even if it spreads across - multiple lines. - -3.5.1. Example - - my-node 1 2 3 a b c - -3.6. Children Block - - A children block is a block of Nodes (Section 3.2), surrounded by { - and }. They are an optional part of nodes, and create a hierarchy of - KDL nodes. - - Regular node termination rules apply, which means multiple nodes can - be included in a single-line children block, as long as they're all - terminated by ;. - -3.6.1. Example - - parent { - child1 - child2 - } - - parent { child1; child2; } - -3.7. Value - - A value is either: a String (Section 3.9), a Number (Section 3.14), a - Boolean (Section 3.15), or Null (Section 3.16). - - Values _MUST_ be either Arguments (Section 3.5) or values of - Properties (Section 3.4). Only String (Section 3.9) values may be - used as Node (Section 3.2) names or Property (Section 3.4) keys. - - Values (both as arguments and in properties) _MAY_ be prefixed by a - single Type Annotation (Section 3.8). - -3.8. Type Annotation - - A type annotation is a prefix to any Node Name (Section 3.2) or Value - (Section 3.7) that includes a _suggestion_ of what type the value is - _intended_ to be treated as, or as a _context-specific elaboration_ - of the more generic type the node name indicates. - - Type annotations are written as a set of ( and ) with a single String - (Section 3.9) in it. It may contain Whitespace after the ( and - before the ), and may be separated from its target by Whitespace. - - KDL does not specify any restrictions on what implementations might - do with these annotations. They are free to ignore them, or use them - to make decisions about how to interpret a value. - - Additionally, the following type annotations MAY be recognized by KDL - parsers and, if used, SHOULD interpret these types as follows: - -3.8.1. Reserved Type Annotations for Numbers Without Decimals: - - Signed integers of various sizes (the number is the bit size): - - * i8 - - * i16 - - * i32 - - * i64 - - * i128 - - Unsigned integers of various sizes (the number is the bit size): - - * u8 - - * u16 - - * u32 - - * u64 - - * u128 - - Platform-dependent integer types, both signed and unsigned: - - * isize - - * usize - -3.8.2. Reserved Type Annotations for Numbers With Decimals: - - IEEE 754 floating point numbers, both single (32) and double (64) - precision: - - * f32 - - * f64 - - IEEE 754-2008 decimal floating point numbers - - * decimal64 - - * decimal128 - -3.8.3. Reserved Type Annotations for Strings: - - * date-time: ISO8601 date/time format. - - * time: "Time" section of ISO8601. - - * date: "Date" section of ISO8601. - - * duration: ISO8601 duration format. - - * decimal: IEEE 754-2008 decimal string format. - - * currency: ISO 4217 currency code. - - * country-2: ISO 3166-1 alpha-2 country code. - - * country-3: ISO 3166-1 alpha-3 country code. - - * country-subdivision: ISO 3166-2 country subdivision code. - - * email: RFC5322 email address. - - * idn-email: RFC6531 internationalized email address. - - * hostname: RFC1123 internet hostname (only ASCII segments) - - * idn-hostname: RFC5890 internationalized internet hostname (only xn - ---prefixed ASCII "punycode" segments, or non-ASCII segments) - - * ipv4: RFC2673 dotted-quad IPv4 address. - - * ipv6: RFC2373 IPv6 address. - - * url: RFC3986 URI. - - * url-reference: RFC3986 URI Reference. - - * irl: RFC3987 Internationalized Resource Identifier. - - * irl-reference: RFC3987 Internationalized Resource Identifier - Reference. - - * url-template: RFC6570 URI Template. - - * uuid: RFC4122 UUID. - - * regex: Regular expression. Specific patterns may be - implementation-dependent. - - * base64: A Base64-encoded string, denoting arbitrary binary data. - -3.8.4. Examples - - node (u8)123 - node prop=(regex).* - (published)date "1970-01-01" - (contributor)person name="Foo McBar" - -3.9. String - - Strings in KDL represent textual UTF-8 Values (Section 3.7). A - String is either an Identifier String (Section 3.10) (like foo), a - Quoted String (Section 3.11) (like "foo") or a Multi-Line String - (Section 3.12). Both Quoted and Multiline strings come in normal and - Raw String (Section 3.13) variants (like #"foo"#): - - * Identifier Strings let you write short, "single-word" strings with - a minimum of syntax - - * Quoted Strings let you write strings "like normal", with - whitespace and escapes. - - * Multi-Line Strings let you write strings across multiple lines and - with indentation that's not part of the string value. - - * Raw Strings don't allow any escapes, allowing you to not worry - about the string's content containing anything that might look - like an escape. - - Strings _MUST_ be represented as UTF-8 values. - - Strings _MUST NOT_ include the code points for disallowed literal - code points (Section 3.19) directly. Quoted and Multi-Line Strings - may include these code points as _values_ by representing them with - their corresponding \u{...} escape. - -3.10. Identifier String - - An Identifier String (sometimes referred to as just an "identifier") - is composed of any Unicode Scalar Value (https://unicode.org/ - glossary/#unicode_scalar_value) other than non-initial characters - (Section 3.10.1), followed by any number of Unicode Scalar Values - other than non-identifier characters (Section 3.10.2). - - A handful of patterns are disallowed, to avoid confusion with other - values: - - * idents that appear to start with a Number (Section 3.14) (like - 1.0v2 or -1em) or the "almost a number" pattern of a decimal point - without a leading digit (like .1). - - * idents that are the language keywords (inf, -inf, nan, true, - false, and null) without their leading #. - - Identifiers that match these patterns _MUST_ be treated as a syntax - error; such values can only be written as quoted or raw strings. The - precise details of the identifier syntax is specified in the Full - Grammar in Section 4. - -3.10.1. Non-initial characters - - The following characters cannot be the first character in an - Identifier String (Section 3.10): - - * Any decimal digit (0-9) - - * Any non-identifier characters (Section 3.10.2) - - Additionally, the following initial characters impose limitations on - subsequent characters: - - * the + and - characters can only be used as an initial character if - the second character is _not_ a digit. If the second character is - ., then the third character must _not_ be a digit. - - * the . character can only be used as an initial character if the - second character is _not_ a digit. - - This allows identifiers to look like --this or .md, and removes the - ambiguity of having an identifier look like a number. - -3.10.2. Non-identifier characters - - The following characters cannot be used anywhere in a Identifier - String (Section 3.10): - - * Any of (){}[]/\"#;= - - * Any Whitespace (Section 3.17) or Newline (Section 3.18). - - * Any disallowed literal code points (Section 3.19) in KDL - documents. - -3.11. Quoted String - - A Quoted String is delimited by " on either side of any number of - literal string characters except unescaped " and \. - - Literal Newline (Section 3.18) characters can only be included if - they are Escaped Whitespace (Section 3.11.1.1), which discards them - from the string value. Actually including a newline in the value - requires using a newline escape sequence, like \n, or using a Multi- - Line String (Section 3.12) which is actually designed for strings - stretching across multiple lines. - - Like Identifier Strings, Quoted Strings _MUST NOT_ include any of the - disallowed literal code-points (Section 3.19) as code points in their - body. - - Quoted Strings have a Raw String (Section 3.13) variant, which - disallows escapes. - -3.11.1. Escapes - - In addition to literal code points, a number of "escapes" are - supported in Quoted Strings. "Escapes" are the character \ followed - by another character, and are interpreted as described in the - following table: - - +==============+=========+=========================================+ - | Name | Escape | Code Pt | - +==============+=========+=========================================+ - | Line Feed | \n | U+000A | - +--------------+---------+-----------------------------------------+ - | Carriage | \r | U+000D | - | Return | | | - +--------------+---------+-----------------------------------------+ - | Character | \t | U+0009 | - | Tabulation | | | - | (Tab) | | | - +--------------+---------+-----------------------------------------+ - | Reverse | \\ | U+005C | - | Solidus | | | - | (Backslash) | | | - +--------------+---------+-----------------------------------------+ - | Quotation | \" | U+0022 | - | Mark (Double | | | - | Quote) | | | - +--------------+---------+-----------------------------------------+ - | Backspace | \b | U+0008 | - +--------------+---------+-----------------------------------------+ - | Form Feed | \f | U+000C | - +--------------+---------+-----------------------------------------+ - | Space | \s | U+0020 | - +--------------+---------+-----------------------------------------+ - | Unicode | \u{(1-6 | Code point described by hex characters, | - | Escape | hex | as long as it represents a Unicode | - | | chars)} | Scalar Value (https://unicode.org/ | - | | | glossary/#unicode_scalar_value) | - +--------------+---------+-----------------------------------------+ - | Whitespace | See | N/A | - | Escape | below | | - +--------------+---------+-----------------------------------------+ - - Table 1 - -3.11.1.1. Escaped Whitespace - - In addition to escaping individual characters, \ can also escape - whitespace. When a \ is followed by one or more literal whitespace - characters, the \ and all of that whitespace are discarded. For - example, - - "Hello World" - - and - - "Hello \ World" - - are semantically identical. See whitespace (Section 3.17) and - newlines (Section 3.18) for how whitespace is defined. - - Note that only literal whitespace is escaped; whitespace escapes (\n - and such) are retained. For example, these strings are all - semantically identical: - - "Hello\ \nWorld" - - "Hello\n\ - World" - - "Hello\nWorld" - - """ - Hello - World - """ - -3.11.1.2. Invalid escapes - - Except as described in the escapes table, above, \ _MUST NOT_ precede - any other characters in a string. - -3.12. Multi-line String - - Multi-Line Strings support multiple lines with literal, non-escaped - Newlines. They must use a special multi-line syntax, and they - automatically "dedent" the string, allowing its value to be indented - to a visually matching level as desired. - - A Multi-Line String is opened and closed by _three_ double-quote - characters, like """. Its first line _MUST_ immediately start with a - Newline (Section 3.18) after its opening """. Its final line _MUST_ - contain only whitespace before the closing """. All in-between lines - that contain non-newline, non-whitespace characters _MUST_ start with - _at least_ the exact same whitespace as the final line (precisely - matching codepoints, not merely counting characters or "size"); they - may contain additional whitespace following this prefix. The lines - in between may contain unescaped " (but no unescaped """ as this - would close the string). - - The value of the Multi-Line String omits the first and last Newline, - the Whitespace of the last line, and the matching Whitespace prefix - on all intermediate lines. The first and last Newline can be the - same character (that is, empty multi-line strings are legal). - - In other words, the final line specifies the whitespace prefix that - will be removed from all other lines. - - Multi-line Strings that do not immediately start with a Newline and - whose final """ is not preceeded by optional whitespace and a Newline - are illegal. This also means that """ may not be used for a single- - line String (e.g. """foo"""). - -3.12.1. Newline Normalization - - Literal Newline sequences in Multi-line Strings must be normalized to - a single U+000A (LF) during deserialization. This means, for - example, that CR LF becomes a single LF during parsing. - - This normalization does not apply to non-literal Newlines entered - using escape sequences. That is: - - multi-line """ - \r\n[CRLF] - foo[CRLF] - """ - - becomes: - - single-line "\r\n\nfoo" - - For clarity: this normalization applies to each individual Newline - sequence. That is, the literal sequence CRLF CRLF becomes LF LF, not - LF. - -3.12.2. Examples - -3.12.2.1. Indented multi-line string - - multi-line """ - foo - This is the base indentation - bar - """ - - This example's string value will be: - - foo - This is the base indentation - bar - - which is equivalent to - - " foo\nThis is the base indentation\n bar" - - when written as a single-line string. - -3.12.2.2. Shorter last-line indent - - If the last line wasn't indented as far, it won't dedent the rest of - the lines as much: - - multi-line """ - foo - This is no longer on the left edge - bar - """ - - This example's string value will be: - - foo - This is no longer on the left edge - bar - - Equivalent to - - " foo\n This is no longer on the left edge\n bar" - -3.12.2.3. Empty lines - - Empty lines can contain any whitespace, or none at all, and will be - reflected as empty in the value: - - multi-line """ - Indented a bit - - A second indented paragraph. - """ - - This example's string value will be: - - Indented a bit. - - A second indented paragraph. - - Equivalent to - - "Indented a bit.\n\nA second indented paragraph." - -3.12.2.4. Syntax errors - - The following yield *syntax errors*: - - multi-line """can't be single line""" - - multi-line """ - closing quote with non-whitespace prefix""" - - multi-line """stuff - """ - - // Every line must share the exact same prefix as the closing line. - multi-line """[\n] - [tab]a[\n] - [space][space]b[\n] - [space][tab][\n] - [tab]""" - -3.12.3. Interaction with Whitespace Escapes - - Multi-line strings support the same mechanism for escaping whitespace - as Quoted Strings. - - When processing a Multi-line String, implementations MUST dedent the - string _after_ resolving all whitespace escapes, but _before_ - resolving other backslash escapes. This means a whitespace escape - that attempts to escape the final line's newline and/or whitespace - prefix can be invalid: if removing escaped whitespace places the - closing """ on a line with non-whitespace characters, this escape is - invalid. - - For example, the following example is illegal: - - """ - foo - bar\ - """ - - // equivalent to - """ - foo - bar""" - - while the following example is allowed - - """ - foo \ - bar - baz - \ """ - - // equivalent to - """ - foo bar - baz - """ - -3.13. Raw String - - Both Quoted (Section 3.11) and Multi-Line Strings (Section 3.12) have - Raw String variants, which are identical in syntax except they do not - support \-escapes. This includes line-continuation escapes (\ + ws - collapsing to nothing). They otherwise share the same properties as - far as literal Newline (Section 3.18) characters go, multi-line - rules, and the requirement of UTF-8 representation. - - The Raw String variants are indicated by preceding the strings's - opening quotes with one or more # characters. The string is then - closed by its normal closing quotes, followed by a _matching_ number - of # characters. This means that the string may contain any - combination of " and # characters other than its closing delimiter - (e.g., if a raw string starts with ##", it can contain " or "#, but - not "## or "###). - - Like other Strings, Raw Strings _MUST NOT_ include any of the - disallowed literal code-points (Section 3.19) as code points in their - body. Unlike with Quoted Strings, these cannot simply be escaped, - and are thus unrepresentable when using Raw Strings. - -3.13.1. Example - - just-escapes #"\n will be literal"# - - The string contains the literal characters \n will be literal. - - quotes-and-escapes ##"hello\n\r\asd"#world"## - - The string contains the literal characters hello\n\r\asd"#world - - raw-multi-line #""" - Here's a """ - multiline string - """ - without escapes. - """# - - The string contains the value - - Here's a """ - multiline string - """ - without escapes. - - or equivalently, - - "Here's a \"\"\"\n multiline string\n \"\"\"\nwithout escapes." - - as a Quoted String. - -3.14. Number - - Numbers in KDL represent numerical Values (Section 3.7). There is no - logical distinction in KDL between real numbers, integers, and - floating point numbers. It's up to individual implementations to - determine how to represent KDL numbers. - - There are five syntaxes for Numbers: Keywords, Decimal, Hexadecimal, - Octal, and Binary. - - * All non-Keyword (Section 3.14.1) numbers may optionally start with - one of - or +, which determine whether they'll be positive or - negative. - - * Binary numbers start with 0b and only allow 0 and 1 as digits, - which may be separated by _. They represent numbers in radix 2. - - * Octal numbers start with 0o and only allow digits between 0 and 7, - which may be separated by _. They represent numbers in radix 8. - - * Hexadecimal numbers start with 0x and allow digits between 0 and - 9, as well as letters A through F, in either lower or upper case, - which may be separated by _. They represent numbers in radix 16. - - * Decimal numbers are a bit more special: - - - They have no radix prefix. - - - They use digits 0 through 9, which may be separated by _. - - - They may optionally include a decimal separator ., followed by - more digits, which may again be separated by _. - - - They may optionally be followed by E or e, an optional - or +, - and more digits, to represent an exponent value. - - Note that, similar to JSON and some other languages, numbers without - an integer digit (such as .1) are illegal. They must be written with - at least one integer digit, like 0.1. (These patterns are also - disallowed from Identifier Strings (Section 3.10), to avoid - confusion.) - -3.14.1. Keyword Numbers - - There are three special "keyword" numbers included in KDL to - accomodate the widespread use of IEEE 754 - (https://en.wikipedia.org/wiki/IEEE_754) floats: - - * #inf - floating point positive infinity. - - * #-inf - floating point negative infinity. - - * #nan - floating point NaN/Not a Number. - - To go along with this and prevent foot guns, the bare Identifier - Strings (Section 3.10) inf, -inf, and nan are considered illegal - identifiers and should yield a syntax error. - - The existence of these keywords does not imply that any numbers be - represented as IEEE 754 floats. These are simply for clarity and - convenience for any implementation that chooses to represent their - numbers in this way. - -3.15. Boolean - - A boolean Value (Section 3.7) is either the symbol #true or #false. - These _SHOULD_ be represented by implementation as boolean logical - values, or some approximation thereof. - -3.15.1. Example - - my-node #true value=#false - -3.16. Null - - The symbol #null represents a null Value (Section 3.7). It's up to - the implementation to decide how to represent this, but it generally - signals the "absence" of a value. - -3.16.1. Example - - my-node #null key=#null - -3.17. Whitespace - - The following characters should be treated as non-Newline - (Section 3.18) white space - (https://www.unicode.org/Public/UCD/latest/ucd/PropList.txt): - - +===========================+=========+ - | Name | Code Pt | - +===========================+=========+ - | Character Tabulation | U+0009 | - +---------------------------+---------+ - | Space | U+0020 | - +---------------------------+---------+ - | No-Break Space | U+00A0 | - +---------------------------+---------+ - | Ogham Space Mark | U+1680 | - +---------------------------+---------+ - | En Quad | U+2000 | - +---------------------------+---------+ - | Em Quad | U+2001 | - +---------------------------+---------+ - | En Space | U+2002 | - +---------------------------+---------+ - | Em Space | U+2003 | - +---------------------------+---------+ - | Three-Per-Em Space | U+2004 | - +---------------------------+---------+ - | Four-Per-Em Space | U+2005 | - +---------------------------+---------+ - | Six-Per-Em Space | U+2006 | - +---------------------------+---------+ - | Figure Space | U+2007 | - +---------------------------+---------+ - | Punctuation Space | U+2008 | - +---------------------------+---------+ - | Thin Space | U+2009 | - +---------------------------+---------+ - | Hair Space | U+200A | - +---------------------------+---------+ - | Narrow No-Break Space | U+202F | - +---------------------------+---------+ - | Medium Mathematical Space | U+205F | - +---------------------------+---------+ - | Ideographic Space | U+3000 | - +---------------------------+---------+ - - Table 2 - -3.17.1. Single-line comments - - Any text after //, until the next literal Newline (Section 3.18) is - "commented out", and is considered to be Whitespace (Section 3.17). - -3.17.2. Multi-line comments - - In addition to single-line comments using //, comments can also be - started with /* and ended with */. These comments can span multiple - lines. They are allowed in all positions where Whitespace - (Section 3.17) is allowed and can be nested. - -3.17.3. Slashdash comments - - Finally, a special kind of comment called a "slashdash", denoted by - /-, can be used to comment out entire _components_ of a KDL document - logically, and have those elements not be included as part of the - parsed document data. - - Slashdash comments can be used before the following, including before - their type annotations, if present: - - * A Node (Section 3.2): the entire Node is treated as Whitespace, - including all props, args, and children. - - * An Argument (Section 3.5): the Argument value is treated as - Whitespace. - - * A Property (Section 3.4) key: the entire property, including both - key and value, is treated as Whitespace. A slashdash of just the - property value is not allowed. - - * A Children Block (Section 3.6): the entire block, including all - children within, is treated as Whitespace. Only other children - blocks, whether slashdashed or not, may follow a slashdashed - children block. - - A slashdash may be be followed by any amount of whitespace, including - newlines and comments (other than other slashdashes), before the - element that it comments out. - -3.18. Newline - - The following character sequences should be treated as new lines - (https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter- - 5/#G41643): - - +=========+===============================+=================+ - | Acronym | Name | Code Pt | - +=========+===============================+=================+ - | CRLF | Carriage Return and Line Feed | U+000D + U+000A | - +---------+-------------------------------+-----------------+ - | CR | Carriage Return | U+000D | - +---------+-------------------------------+-----------------+ - | LF | Line Feed | U+000A | - +---------+-------------------------------+-----------------+ - | NEL | Next Line | U+0085 | - +---------+-------------------------------+-----------------+ - | VT | Vertical tab | U+000B | - +---------+-------------------------------+-----------------+ - | FF | Form Feed | U+000C | - +---------+-------------------------------+-----------------+ - | LS | Line Separator | U+2028 | - +---------+-------------------------------+-----------------+ - | PS | Paragraph Separator | U+2029 | - +---------+-------------------------------+-----------------+ - - Table 3 - - Note that for the purpose of new lines, the specific sequence CRLF is - considered _a single newline_. - -3.19. Disallowed Literal Code Points - - The following code points may not appear literally anywhere in the - document. They may be represented in Strings (but not Raw Strings) - using Unicode Escapes (Section 3.11.1) (\u{...}, except for non - Unicode Scalar Value, which can't be represented even as escapes). - - * The codepoints U+0000-0008 or the codepoints U+000E-001F (various - control characters). - - * U+007F (the Delete control character). - - * Any codepoint that is not a Unicode Scalar Value - (https://unicode.org/glossary/#unicode_scalar_value) - (U+D800-DFFF). - - * U+200E-200F, U+202A-202E, and U+2066-2069, the unicode "direction - control" characters (https://www.w3.org/International/questions/ - qa-bidi-unicode-controls) - - * U+FEFF, aka Zero-width Non-breaking Space (ZWNBSP)/Byte Order Mark - (BOM), except as the first code point in a document. - -4. Full Grammar - - This is the full official grammar for KDL and should be considered - authoritative if something seems to disagree with the text above. - The grammar language syntax is defined in Section 4.1. - - document := bom? version? nodes - - // Nodes - nodes := (line-space* node)* line-space* - - base-node := slashdash? type? node-space* string - (node-space+ slashdash? node-prop-or-arg)* - // slashdashed node-children must always be after props and args. - (node-space+ slashdash node-children)* - (node-space+ node-children)? - (node-space+ slashdash node-children)* - node-space* - node := base-node node-terminator - final-node := base-node node-terminator? - - // Entries - node-prop-or-arg := prop | value - node-children := '{' nodes final-node? '}' - node-terminator := single-line-comment | newline | ';' | eof - - prop := string node-space* '=' node-space* value - value := type? node-space* (string | number | keyword) - type := '(' node-space* string node-space* ')' - - // Strings - string := identifier-string | quoted-string | raw-string ¶ - - identifier-string := unambiguous-ident | signed-ident | dotted-ident - unambiguous-ident := - ((identifier-char - digit - sign - '.') identifier-char*) - - disallowed-keyword-strings - signed-ident := - sign ((identifier-char - digit - '.') identifier-char*)? - dotted-ident := - sign? '.' ((identifier-char - digit) identifier-char*)? - identifier-char := - unicode - unicode-space - newline - [\\/(){};\[\]"#=] - - disallowed-literal-code-points - disallowed-keyword-identifiers := - 'true' | 'false' | 'null' | 'inf' | '-inf' | 'nan' - - quoted-string := - '"' single-line-string-body '"' | - '"""' newline - (multi-line-string-body newline)? - (unicode-space | ws-escape)* '"""' - single-line-string-body := (string-character - newline)* - multi-line-string-body := (('"' | '""')? string-character)* - string-character := - '\\' (["\\bfnrts] | - 'u{' hex-unicode '}') | - ws-escape | - [^\\"] - disallowed-literal-code-points - ws-escape := '\\' (unicode-space | newline)+ - hex-digit := [0-9a-fA-F] - hex-unicode := hex-digit{1, 6} - surrogate - above-max-scalar // Unicode Scalar Value in hex₁₆, leading 0s allowed within length ≤ 6 - surrogate := [0]{0, 2} [dD] [8-9a-fA-F] hex-digit{2} - // U+D800-DFFF: D 8 00 - // D F FF - above-max-scalar = [2-9a-fA-F] hex-digit{5} | [1] [1-9a-fA-F] hex-digit{4} - // >U+10FFFF: >1 _____ 1 >0 ____ - - - raw-string := '#' raw-string-quotes '#' | '#' raw-string '#' - raw-string-quotes := - '"' single-line-raw-string-body '"' | - '"""' newline - (multi-line-raw-string-body newline)? - unicode-space* '"""' - single-line-raw-string-body := - '' | - (single-line-raw-string-char - '"') - single-line-raw-string-char*? | - '"' (single-line-raw-string-char - '"') - single-line-raw-string-char*? - single-line-raw-string-char := - unicode - newline - disallowed-literal-code-points - multi-line-raw-string-body := - (unicode - disallowed-literal-code-points)*? - - // Numbers - number := keyword-number | hex | octal | binary | decimal - - decimal := sign? integer ('.' integer)? exponent? - exponent := ('e' | 'E') sign? integer - integer := digit (digit | '_')* - digit := [0-9] - sign := '+' | '-' - - hex := sign? '0x' hex-digit (hex-digit | '_')* - octal := sign? '0o' [0-7] [0-7_]* - binary := sign? '0b' ('0' | '1') ('0' | '1' | '_')* - - // Keywords and booleans. - keyword := boolean | '#null' - keyword-number := '#inf' | '#-inf' | '#nan' - boolean := '#true' | '#false' - - // Specific code points - bom := '\u{FEFF}' - disallowed-literal-code-points := - See Table (Disallowed Literal Code Points) - unicode := Any Unicode Scalar Value - unicode-space := See Table - (All White_Space unicode characters which are not `newline`) - - // Comments - single-line-comment := '//' ^newline* (newline | eof) - multi-line-comment := '/*' commented-block - commented-block := - '*/' | (multi-line-comment | '*' | '/' | [^*/]+) commented-block - slashdash := '/-' line-space* - - // Whitespace - ws := unicode-space | multi-line-comment - escline := '\\' ws* (single-line-comment | newline | eof) - newline := See Table (All Newline White_Space) - // Whitespace where newlines are allowed. - line-space := node-space | newline | single-line-comment - // Whitespace within nodes, - // where newline-ish things must be esclined. - node-space := ws* escline ws* | ws+ - - // Version marker - version := - '/-' unicode-space* 'kdl-version' unicode-space+ ('1' | '2') - unicode-space* newline - -4.1. Grammar language - - The grammar language syntax is a combination of ABNF with some regex - spice thrown in. Specifically: - - * Single quotes (') are used to denote literal text. \ within a - literal string is used for escaping other single-quotes, for - initiating unicode characters using hex values (\u{FEFF}), and for - escaping \ itself (\\). - - * * is used for "zero or more", + is used for "one or more", and ? - is used for "zero or one". Per standard regex semantics, * and + - are _greedy_; they match as many instances as possible without - failing the match. - - * *? (used only in raw strings) indicates a _non-greedy_ match; it - matches as _few_ instances as possible without failing the match. - - * ¶ is a _cut point_. It always matches and consumes no characters, - but once matched, the parser is not allowed to backtrack past that - point in the source. If a parser would rewind past the cut point, - it must instead fail the overall parse, as if it had run out of - options. (This is only used with the raw-string production, to - ensure the first instance of the appropriate closing quote - sequence is guaranteed to be the end of the raw string, rather - than allowing it to potentially consume more of the document - unexpectedly.) - - * () can be used to group matches that must be matched together. - - * a | b means a or b, whichever matches first. If multiple items - are before a |, they are a single group. a b c | d is equivalent - to (a b c) | d. - - * [] are used for regex-style character matches, where any character - between the brackets will be a single match. \ is used to escape - \, [, and ]. They also support character ranges (0-9), and - negation (^) - - * - is used for "except for" or "minus" whatever follows it. For - example, a - 'x' means "any a, except something that matches the - literal 'x'". - - * The prefix ^ means "something that does not match" whatever - follows it. For example, ^foo means "must not match foo". - - * A single definition may be split over multiple lines. Newlines - are treated as spaces. - - * // followed by text on its own line is used as comment syntax. - -Authors' Addresses - - Katerina Zoé Marchán Salvá - Microsoft - - - The KDL Contributors diff --git a/zkat/minor-tweaks/index.html b/zkat/minor-tweaks/index.html deleted file mode 100644 index ca5829a..0000000 --- a/zkat/minor-tweaks/index.html +++ /dev/null @@ -1,45 +0,0 @@ - - - - kdl-org/kdl zkat/minor-tweaks preview - - - - -

Editor's drafts for zkat/minor-tweaks branch of kdl-org/kdl

- - - - - - -
KDLplain textsame as main
- - - diff --git a/zkat/schema-v2/draft-marchan-kdl2.html b/zkat/suffixes/draft-marchan-kdl2.html similarity index 89% rename from zkat/schema-v2/draft-marchan-kdl2.html rename to zkat/suffixes/draft-marchan-kdl2.html index eb0de0e..5956dd4 100644 --- a/zkat/schema-v2/draft-marchan-kdl2.html +++ b/zkat/suffixes/draft-marchan-kdl2.html @@ -20,17 +20,17 @@ oficial version of the language, see https://kdl.dev/spec. " name="description"> - + - - - - - - - - - - - - - - - - - -
KDLJanuary 2025
Marchán & KDL ContributorsExperimental[Page]
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Workgroup:
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KDL Community
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Published:
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Authors:
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K. Marchán
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Microsoft
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KDL Contributors
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The KDL Document Language

-
-

Abstract

-

KDL is a node-oriented document language. Its niche and purpose overlaps with -XML, and as do many of its semantics. You can use KDL both as a configuration -language, and a data exchange or storage format, if you so choose.

-

This is the formal specification for KDL, including the intended data model and -the grammar.

-

This document describes KDL version KDL 2.0.0. It was released on 2024-12-21. It -is the latest stable version of the language, and will only be edited for minor -copyedits or major errata.

-
-
-

-About This Document -

-

This note is to be removed before publishing as an RFC.

-

- Status information for this document may be found at https://datatracker.ietf.org/doc/draft-marchan-kdl2/.

-

- information can be found at https://kdl.dev/.

-

Source for this draft and an issue tracker can be found at - https://github.com/kdl-org/kdl.

-
-
-

-License -

-

This work is licensed under Creative Commons Attribution-ShareAlike 4.0 -International. To view a copy of this license, visit -https://creativecommons.org/licenses/by-sa/4.0/

-
-
-
- ▲

-Table of Contents -

- -
-
-
-
-

-1. Compatibility -

-

KDL 2.0 is designed such that for any given KDL document written as KDL -1.0 or KDL 2.0, the parse will either fail completely, or, if the -parse succeeds, the data represented by a v1 or v2 parser will be identical. -This means that it's safe to use a fallback parsing strategy in order to support -both v1 and v2 simultaneously. For example, node "foo" is a valid node in both -versions, and should be represented identically by parsers.

-

A version marker /- kdl-version 2 (or 1) MAY be added to the beginning of -a KDL document, optionally preceded by the BOM, and parsers MAY use that as a -hint as to which version to parse the document as.

-
-
-
-
-

-2. Introduction -

-

KDL is a node-oriented document language. Its niche and purpose overlaps with -XML, and as do many of its semantics. You can use KDL both as a configuration -language, and a data exchange or storage format, if you so choose.

-

The bulk of this document is dedicated to a long-form description of all -Components (Section 3) of a KDL document. -There is also a much more terse -Grammar (Section 4) at the end of the document that covers most of the -rules, with some semantic exceptions involving the data model.

-

KDL is designed to be easy to read and easy to implement.

-

In this document, references to "left" or "right" refer to directions in the -data stream towards the beginning or end, respectively; in other words, -the directions if the data stream were only ASCII text. They do not refer -to the writing direction of text, which can flow in either direction, -depending on the characters used.

-
-
-
-
-

-3. Components -

-
-
-

-3.1. Document -

-

The toplevel concept of KDL is a Document. A Document is composed of zero or -more Nodes (Section 3.2), separated by newlines and whitespace, and eventually -terminated by an EOF.

-

All KDL documents MUST be encoded in UTF-8 and conform to the specifications in -this document.

-
-
-

-3.1.1. Example -

-

The following is a document composed of two toplevel nodes:

-
-
-foo {
-    bar
-}
-baz
-
-
-
-
-
-
-
-
-

-3.2. Node -

-

Being a node-oriented language means that the real core component of any KDL -document is the "node". Every node must have a name, which must be a -String (Section 3.9).

-

The name may be preceded by a Type Annotation (Section 3.8) to further -clarify its type, particularly in relation to its parent node. (For example, -clarifying that a particular date child node is for the publication date, -rather than the last-modified date, with (published)date.)

-

Following the name are zero or more Arguments (Section 3.5) or -Properties (Section 3.4), separated by either whitespace (Section 3.17) or a -slash-escaped line continuation (Section 3.3). Arguments and Properties -may be interspersed in any order, much like is common with positional arguments -vs options in command line tools. Collectively, Arguments and Properties may be -referred to as "Entries".

-

Children (Section 3.6) can be placed after the name and the optional -Entries, possibly separated by either whitespace or a -slash-escaped line continuation.

-

Arguments are ordered relative to each other and that order must be preserved in -order to maintain the semantics. Properties between Arguments do not affect -Argument ordering.

-

By contrast, Properties SHOULD NOT be assumed to be presented in a given -order. Children (Section 3.6) should be used if an order-sensitive -key/value data structure must be represented in KDL. Cf. JSON objects -preserving key order.

-

Nodes MAY be prefixed with Slashdash (Section 3.17.3) to "comment out" -the entire node, including its properties, arguments, and children, and make -it act as plain whitespace, even if it spreads across multiple lines.

-

Finally, a node is terminated by either a Newline (Section 3.18), a semicolon -(;), the end of a child block (}) or the end of the file/stream (an EOF).

-
-
-

-3.2.1. Example -

-
-
-// `foo` will have an Argument value list like `[1, 3]`.
-foo 1 key=val 3 {
-    bar
-    (role)baz 1 2
-}
-
-
-
-
-
-
-
-
-

-3.3. Line Continuation -

-

Line continuations allow Nodes (Section 3.2) to be spread across multiple lines.

-

A line continuation is a \ character followed by zero or more whitespace -items (including multiline comments) and an optional single-line comment. It -must be terminated by a Newline (Section 3.18) (including the Newline that is -part of single-line comments).

-

Following a line continuation, processing of a Node can continue as usual.

-
-
-

-3.3.1. Example -

-
-
-my-node 1 2 \  // comments are ok after \
-        3 4    // This is the actual end of the Node.
-
-
-
-
-
-
-
-
-

-3.4. Property -

-

A Property is a key/value pair attached to a Node (Section 3.2). A Property is -composed of a String (Section 3.9), followed immediately by an equals sign (=, U+003D), -and then a Value (Section 3.7).

-

Properties should be interpreted left-to-right, with rightmost properties with -identical names overriding earlier properties. That is:

-
-
-node a=1 a=2
-
-
-

In this example, the node's a value must be 2, not 1.

-

No other guarantees about order should be expected by implementers. -Deserialized representations may iterate over properties in any order and -still be spec-compliant.

-

Properties MAY be prefixed with /- to "comment out" the entire token and -make it act as plain whitespace, even if it spreads across multiple lines.

-
-
-
-
-

-3.5. Argument -

-

An Argument is a bare Value (Section 3.7) attached to a Node (Section 3.2), with no -associated key. It shares the same space as Properties (Section 3.4), and may be interleaved with them.

-

A Node may have any number of Arguments, which should be evaluated left to -right. KDL implementations MUST preserve the order of Arguments relative to -each other (not counting Properties).

-

Arguments MAY be prefixed with /- to "comment out" the entire token and -make it act as plain whitespace, even if it spreads across multiple lines.

-
-
-

-3.5.1. Example -

-
-
-my-node 1 2 3 a b c
-
-
-
-
-
-
-
-
-

-3.6. Children Block -

-

A children block is a block of Nodes (Section 3.2), surrounded by { and }. They -are an optional part of nodes, and create a hierarchy of KDL nodes.

-

Regular node termination rules apply, which means multiple nodes can be -included in a single-line children block, as long as they're all terminated by -;.

-
-
-

-3.6.1. Example -

-
-
-parent {
-    child1
-    child2
-}
-
-parent { child1; child2; }
-
-
-
-
-
-
-
-
-

-3.7. Value -

-

A value is either: a String (Section 3.9), a Number (Section 3.14), a -Boolean (Section 3.15), or Null (Section 3.16).

-

Values MUST be either Arguments (Section 3.5) or values of -Properties (Section 3.4). Only String (Section 3.9) values may be used as -Node (Section 3.2) names or Property (Section 3.4) keys.

-

Values (both as arguments and in properties) MAY be prefixed by a single -Type Annotation (Section 3.8).

-
-
-
-
-

-3.8. Type Annotation -

-

A type annotation is a prefix to any Node Name (Section 3.2) or Value (Section 3.7) that -includes a suggestion of what type the value is intended to be treated as, -or as a context-specific elaboration of the more generic type the node name -indicates.

-

Type annotations are written as a set of ( and ) with a single -String (Section 3.9) in it. It may contain Whitespace after the ( and before -the ), and may be separated from its target by Whitespace.

-

KDL does not specify any restrictions on what implementations might do with -these annotations. They are free to ignore them, or use them to make decisions -about how to interpret a value.

-

Additionally, the following type annotations MAY be recognized by KDL parsers -and, if used, SHOULD interpret these types as follows:

-
-
-

-3.8.1. Reserved Type Annotations for Numbers Without Decimals: -

-

Signed integers of various sizes (the number is the bit size):

-
    -
  • -

    i8

    -
    • -
  • -

    i16

    -
    • -
  • -

    i32

    -
    • -
  • -

    i64

    -
    • -
  • -

    i128

    -
    • -
-

Unsigned integers of various sizes (the number is the bit size):

-
    -
  • -

    u8

    -
    • -
  • -

    u16

    -
    • -
  • -

    u32

    -
    • -
  • -

    u64

    -
    • -
  • -

    u128

    -
    • -
-

Platform-dependent integer types, both signed and unsigned:

-
    -
  • -

    isize

    -
    • -
  • -

    usize

    -
    • -
-
-
-
-
-

-3.8.2. Reserved Type Annotations for Numbers With Decimals: -

-

IEEE 754 floating point numbers, both single (32) and double (64) precision:

-
    -
  • -

    f32

    -
    • -
  • -

    f64

    -
    • -
-

IEEE 754-2008 decimal floating point numbers

-
    -
  • -

    decimal64

    -
    • -
  • -

    decimal128

    -
    • -
-
-
-
-
-

-3.8.3. Reserved Type Annotations for Strings: -

-
    -
  • -

    date-time: ISO8601 date/time format.

    -
    • -
  • -

    time: "Time" section of ISO8601.

    -
    • -
  • -

    date: "Date" section of ISO8601.

    -
    • -
  • -

    duration: ISO8601 duration format.

    -
    • -
  • -

    decimal: IEEE 754-2008 decimal string format.

    -
    • -
  • -

    currency: ISO 4217 currency code.

    -
    • -
  • -

    country-2: ISO 3166-1 alpha-2 country code.

    -
    • -
  • -

    country-3: ISO 3166-1 alpha-3 country code.

    -
    • -
  • -

    country-subdivision: ISO 3166-2 country subdivision code.

    -
    • -
  • -

    email: RFC5322 email address.

    -
    • -
  • -

    idn-email: RFC6531 internationalized email address.

    -
    • -
  • -

    hostname: RFC1123 internet hostname (only ASCII segments)

    -
    • -
  • -

    idn-hostname: RFC5890 internationalized internet hostname -(only xn---prefixed ASCII "punycode" segments, or non-ASCII segments)

    -
    • -
  • -

    ipv4: RFC2673 dotted-quad IPv4 address.

    -
    • -
  • -

    ipv6: RFC2373 IPv6 address.

    -
    • -
  • -

    url: RFC3986 URI.

    -
    • -
  • -

    url-reference: RFC3986 URI Reference.

    -
    • -
  • -

    irl: RFC3987 Internationalized Resource Identifier.

    -
    • -
  • -

    irl-reference: RFC3987 Internationalized Resource Identifier Reference.

    -
    • -
  • -

    url-template: RFC6570 URI Template.

    -
    • -
  • -

    uuid: RFC4122 UUID.

    -
    • -
  • -

    regex: Regular expression. Specific patterns may be implementation-dependent.

    -
    • -
  • -

    base64: A Base64-encoded string, denoting arbitrary binary data.

    -
    • -
-
-
-
-
-

-3.8.4. Examples -

-
-
-node (u8)123
-node prop=(regex).*
-(published)date "1970-01-01"
-(contributor)person name="Foo McBar"
-
-
-
-
-
-
-
-
-

-3.9. String -

-

Strings in KDL represent textual UTF-8 Values (Section 3.7). A String is either an -Identifier String (Section 3.10) (like foo), a -Quoted String (Section 3.11) (like "foo") -or a Multi-Line String (Section 3.12). -Both Quoted and Multiline strings come in normal -and Raw String (Section 3.13) variants (like #"foo"#):

-
    -
  • -

    Identifier Strings let you write short, "single-word" strings with a -minimum of syntax

    -
    • -
  • -

    Quoted Strings let you write strings "like normal", with whitespace and escapes.

    -
    • -
  • -

    Multi-Line Strings let you write strings across multiple lines - and with indentation that's not part of the string value.

    -
    • -
  • -

    Raw Strings don't allow any escapes, -allowing you to not worry about the string's content containing anything that -might look like an escape.

    -
    • -
-

Strings MUST be represented as UTF-8 values.

-

Strings MUST NOT include the code points for -disallowed literal code points (Section 3.19) directly. -Quoted and Multi-Line Strings may include these code points as values -by representing them with their corresponding \u{...} escape.

-
-
-
-
-

-3.10. Identifier String -

-

An Identifier String (sometimes referred to as just an "identifier") is -composed of any Unicode Scalar -Value other than -non-initial characters (Section 3.10.1), followed by any number of -Unicode Scalar Values other than non-identifier -characters (Section 3.10.2).

-

A handful of patterns are disallowed, to avoid confusion with other values:

-
    -
  • -

    idents that appear to start with a Number (Section 3.14) (like 1.0v2 or - -1em) or the "almost a number" pattern of a decimal point without a - leading digit (like .1).

    -
    • -
  • -

    idents that are the language keywords (inf, -inf, nan, true, -false, and null) without their leading #.

    -
    • -
-

Identifiers that match these patterns MUST be treated as a syntax error; such -values can only be written as quoted or raw strings. The precise details of the -identifier syntax is specified in the Full Grammar in Section 4.

-
-
-

-3.10.1. Non-initial characters -

-

The following characters cannot be the first character in an -Identifier String (Section 3.10):

-
    -
  • -

    Any decimal digit (0-9)

    -
    • -
  • -

    Any non-identifier characters (Section 3.10.2)

    -
    • -
-

Additionally, the following initial characters impose limitations on subsequent -characters:

-
    -
  • -

    the + and - characters can only be used as an initial character if -the second character is not a digit. If the second character is ., then -the third character must not be a digit.

    -
    • -
  • -

    the . character can only be used as an initial character if -the second character is not a digit.

    -
    • -
-

This allows identifiers to look like --this or .md, and removes the -ambiguity of having an identifier look like a number.

-
-
-
-
-

-3.10.2. Non-identifier characters -

-

The following characters cannot be used anywhere in a Identifier String (Section 3.10):

- -
-
-
-
-
-
-

-3.11. Quoted String -

-

A Quoted String is delimited by " on either side of any number of literal -string characters except unescaped " and \.

-

Literal Newline (Section 3.18) characters can only be included -if they are Escaped Whitespace (Section 3.11.1.1), -which discards them from the string value. -Actually including a newline in the value requires using a newline escape sequence, -like \n, -or using a Multi-Line String (Section 3.12) -which is actually designed for strings stretching across multiple lines.

-

Like Identifier Strings, Quoted Strings MUST NOT include any of the -disallowed literal code-points (Section 3.19) as code -points in their body.

-

Quoted Strings have a Raw String (Section 3.13) variant, -which disallows escapes.

-
-
-

-3.11.1. Escapes -

-

In addition to literal code points, a number of "escapes" are supported in Quoted Strings. -"Escapes" are the character \ followed by another character, and are -interpreted as described in the following table:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table 1
NameEscapeCode Pt
Line Feed - \n - - U+000A -
Carriage Return - \r - - U+000D -
Character Tabulation (Tab) - \t - - U+0009 -
Reverse Solidus (Backslash) - \\ - - U+005C -
Quotation Mark (Double Quote) - \" - - U+0022 -
Backspace - \b - - U+0008 -
Form Feed - \f - - U+000C -
Space - \s - - U+0020 -
Unicode Escape - \u{(1-6 hex chars)} -Code point described by hex characters, as long as it represents a Unicode Scalar Value -
Whitespace EscapeSee belowN/A
-
-
-
-3.11.1.1. Escaped Whitespace -
-

In addition to escaping individual characters, \ can also escape whitespace. -When a \ is followed by one or more literal whitespace characters, the \ -and all of that whitespace are discarded. For example,

-
-
-"Hello World"
-
-
-

and

-
-
-"Hello \    World"
-
-
-

are semantically identical. See whitespace (Section 3.17) -and newlines (Section 3.18) for how whitespace is defined.

-

Note that only literal whitespace is escaped; whitespace escapes (\n and -such) are retained. For example, these strings are all semantically identical:

-
-
-"Hello\       \nWorld"
-
-    "Hello\n\
-    World"
-
-"Hello\nWorld"
-
-"""
-  Hello
-  World
-  """
-
-
-
-
-
-
-
-3.11.1.2. Invalid escapes -
-

Except as described in the escapes table, above, \ MUST NOT precede any -other characters in a string.

-
-
-
-
-
-
-
-
-

-3.12. Multi-line String -

-

Multi-Line Strings support multiple lines with literal, non-escaped -Newlines. They must use a special multi-line syntax, and they automatically -"dedent" the string, allowing its value to be indented to a visually matching -level as desired.

-

A Multi-Line String is opened and closed by three double-quote characters, -like """. -Its first line MUST immediately start with a Newline (Section 3.18) -after its opening """. -Its final line MUST contain only whitespace -before the closing """. -All in-between lines that contain non-newline, non-whitespace characters -MUST start with at least the exact same whitespace as the final line -(precisely matching codepoints, not merely counting characters or "size"); -they may contain additional whitespace following this prefix. The lines in -between may contain unescaped " (but no unescaped """ as this would close -the string).

-

The value of the Multi-Line String omits the first and last Newline, the -Whitespace of the last line, and the matching Whitespace prefix on all -intermediate lines. The first and last Newline can be the same character (that -is, empty multi-line strings are legal).

-

In other words, the final line specifies the whitespace prefix that will be -removed from all other lines.

-

Multi-line Strings that do not immediately start with a Newline and whose final -""" is not preceeded by optional whitespace and a Newline are illegal. This -also means that """ may not be used for a single-line String (e.g. -"""foo""").

-
-
-

-3.12.1. Newline Normalization -

-

Literal Newline sequences in Multi-line Strings must be normalized to a single -U+000A (LF) during deserialization. This means, for example, that CR LF -becomes a single LF during parsing.

-

This normalization does not apply to non-literal Newlines entered using escape -sequences. That is:

-
-
-multi-line """
-    \r\n[CRLF]
-    foo[CRLF]
-    """
-
-
-

becomes:

-
-
-single-line "\r\n\nfoo"
-
-
-

For clarity: this normalization applies to each individual Newline sequence. -That is, the literal sequence CRLF CRLF becomes LF LF, not LF.

-
-
-
-
-

-3.12.2. Examples -

-
-
-
-3.12.2.1. Indented multi-line string -
-
-
-multi-line """
-        foo
-    This is the base indentation
-            bar
-    """
-
-
-

This example's string value will be:

-
-
-    foo
-This is the base indentation
-        bar
-
-
-

which is equivalent to

-
-
-"    foo\nThis is the base indentation\n        bar"
-
-
-

when written as a single-line string.

-
-
-
-
-
-3.12.2.2. Shorter last-line indent -
-

If the last line wasn't indented as far, -it won't dedent the rest of the lines as much:

-
-
-multi-line """
-        foo
-    This is no longer on the left edge
-            bar
-  """
-
-
-

This example's string value will be:

-
-
-      foo
-  This is no longer on the left edge
-          bar
-
-
-

Equivalent to

-
-
-"      foo\n  This is no longer on the left edge\n          bar"
-
-
-
-
-
-
-
-3.12.2.3. Empty lines -
-

Empty lines can contain any whitespace, or none at all, and will be reflected as empty in the value:

-
-
-multi-line """
-    Indented a bit
-
-    A second indented paragraph.
-    """
-
-
-

This example's string value will be:

-
-
-Indented a bit.
-
-A second indented paragraph.
-
-
-

Equivalent to

-
-
-"Indented a bit.\n\nA second indented paragraph."
-
-
-
-
-
-
-
-3.12.2.4. Syntax errors -
-

The following yield syntax errors:

-
-
-multi-line """can't be single line"""
-
-
-
-
-multi-line """
-  closing quote with non-whitespace prefix"""
-
-
-
-
-multi-line """stuff
-  """
-
-
-
-
-// Every line must share the exact same prefix as the closing line.
-multi-line """[\n]
-[tab]a[\n]
-[space][space]b[\n]
-[space][tab][\n]
-[tab]"""
-
-
-
-
-
-
-
-
-

-3.12.3. Interaction with Whitespace Escapes -

-

Multi-line strings support the same mechanism for escaping whitespace as Quoted -Strings.

-

When processing a Multi-line String, implementations MUST dedent the string -after resolving all whitespace escapes, but before resolving other backslash -escapes. This means a whitespace escape that attempts to escape the final line's -newline and/or whitespace prefix can be invalid: if removing escaped whitespace -places the closing """ on a line with non-whitespace characters, this escape -is invalid.

-

For example, the following example is illegal:

-
-
-  """
-  foo
-  bar\
-  """
-
-  // equivalent to
-  """
-  foo
-  bar"""
-
-
-

while the following example is allowed

-
-
-  """
-  foo \
-bar
-  baz
-  \   """
-
-  // equivalent to
-  """
-  foo bar
-  baz
-  """
-
-
-
-
-
-
-
-
-

-3.13. Raw String -

-

Both Quoted (Section 3.11) and Multi-Line Strings (Section 3.12) have -Raw String variants, which are identical in syntax except they do not support -\-escapes. This includes line-continuation escapes (\ + ws collapsing to -nothing). They otherwise share the same properties as far as literal -Newline (Section 3.18) characters go, multi-line rules, and the requirement of -UTF-8 representation.

-

The Raw String variants are indicated by preceding the strings's opening quotes -with one or more # characters. The string is then closed by its normal closing -quotes, followed by a matching number of # characters. This means that the -string may contain any combination of " and # characters other than its -closing delimiter (e.g., if a raw string starts with ##", it can contain " -or "#, but not "## or "###).

-

Like other Strings, Raw Strings MUST NOT include any of the disallowed -literal code-points (Section 3.19) as code points in their -body. Unlike with Quoted Strings, these cannot simply be escaped, and are thus -unrepresentable when using Raw Strings.

-
-
-

-3.13.1. Example -

-
-
-just-escapes #"\n will be literal"#
-
-
-

The string contains the literal characters \n will be literal.

-
-
-quotes-and-escapes ##"hello\n\r\asd"#world"##
-
-
-

The string contains the literal characters hello\n\r\asd"#world

-
-
-raw-multi-line #"""
-    Here's a """
-        multiline string
-        """
-    without escapes.
-    """#
-
-
-

The string contains the value

-
-
-Here's a """
-    multiline string
-    """
-without escapes.
-
-
-

or equivalently,

-
-
-"Here's a \"\"\"\n    multiline string\n    \"\"\"\nwithout escapes."
-
-
-

as a Quoted String.

-
-
-
-
-
-
-

-3.14. Number -

-

Numbers in KDL represent numerical Values (Section 3.7). There is no logical distinction in KDL -between real numbers, integers, and floating point numbers. It's up to -individual implementations to determine how to represent KDL numbers.

-

There are five syntaxes for Numbers: Keywords, Decimal, Hexadecimal, Octal, and Binary.

-
    -
  • -

    All non-Keyword (Section 3.14.1) numbers may optionally start with one of - or +, which determine whether they'll be positive or negative.

    -
    • -
  • -

    Binary numbers start with 0b and only allow 0 and 1 as digits, which may be separated by _. They represent numbers in radix 2.

    -
    • -
  • -

    Octal numbers start with 0o and only allow digits between 0 and 7, which may be separated by _. They represent numbers in radix 8.

    -
    • -
  • -

    Hexadecimal numbers start with 0x and allow digits between 0 and 9, as well as letters A through F, in either lower or upper case, which may be separated by _. They represent numbers in radix 16.

    -
    • -
  • -

    Decimal numbers are a bit more special:

    -
      -
    • -

      They have no radix prefix.

      -
      • -
    • -

      They use digits 0 through 9, which may be separated by _.

      -
      • -
    • -

      They may optionally include a decimal separator ., followed by more digits, which may again be separated by _.

      -
      • -
    • -

      They may optionally be followed by E or e, an optional - or +, and more digits, to represent an exponent value.

      -
      • -
    -
    • -
-

Note that, similar to JSON and some other languages, -numbers without an integer digit (such as .1) are illegal. -They must be written with at least one integer digit, like 0.1. -(These patterns are also disallowed from Identifier Strings (Section 3.10), to avoid confusion.)

-
-
-

-3.14.1. Keyword Numbers -

-

There are three special "keyword" numbers included in KDL to accomodate the -widespread use of IEEE 754 floats:

-
    -
  • -

    #inf - floating point positive infinity.

    -
    • -
  • -

    #-inf - floating point negative infinity.

    -
    • -
  • -

    #nan - floating point NaN/Not a Number.

    -
    • -
-

To go along with this and prevent foot guns, the bare Identifier -Strings (Section 3.10) inf, -inf, and nan are considered illegal -identifiers and should yield a syntax error.

-

The existence of these keywords does not imply that any numbers be represented -as IEEE 754 floats. These are simply for clarity and convenience for any -implementation that chooses to represent their numbers in this way.

-
-
-
-
-
-
-

-3.15. Boolean -

-

A boolean Value (Section 3.7) is either the symbol #true or #false. These -SHOULD be represented by implementation as boolean logical values, or some -approximation thereof.

-
-
-

-3.15.1. Example -

-
-
-my-node #true value=#false
-
-
-
-
-
-
-
-
-

-3.16. Null -

-

The symbol #null represents a null Value (Section 3.7). It's up to the -implementation to decide how to represent this, but it generally signals the -"absence" of a value.

-
-
-

-3.16.1. Example -

-
-
-my-node #null key=#null
-
-
-
-
-
-
-
-
-

-3.17. Whitespace -

-

The following characters should be treated as non-Newline (Section 3.18) white -space:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table 2
NameCode Pt
Character Tabulation - U+0009 -
Space - U+0020 -
No-Break Space - U+00A0 -
Ogham Space Mark - U+1680 -
En Quad - U+2000 -
Em Quad - U+2001 -
En Space - U+2002 -
Em Space - U+2003 -
Three-Per-Em Space - U+2004 -
Four-Per-Em Space - U+2005 -
Six-Per-Em Space - U+2006 -
Figure Space - U+2007 -
Punctuation Space - U+2008 -
Thin Space - U+2009 -
Hair Space - U+200A -
Narrow No-Break Space - U+202F -
Medium Mathematical Space - U+205F -
Ideographic Space - U+3000 -
-
-
-

-3.17.1. Single-line comments -

-

Any text after //, until the next literal Newline (Section 3.18) is "commented -out", and is considered to be Whitespace (Section 3.17).

-
-
-
-
-

-3.17.2. Multi-line comments -

-

In addition to single-line comments using //, comments can also be started -with /* and ended with */. These comments can span multiple lines. They -are allowed in all positions where Whitespace (Section 3.17) is allowed and -can be nested.

-
-
-
-
-

-3.17.3. Slashdash comments -

-

Finally, a special kind of comment called a "slashdash", denoted by /-, can -be used to comment out entire components of a KDL document logically, and -have those elements not be included as part of the parsed document data.

-

Slashdash comments can be used before the following, including before their type -annotations, if present:

-
    -
  • -

    A Node (Section 3.2): the entire Node is treated as Whitespace, including all -props, args, and children.

    -
    • -
  • -

    An Argument (Section 3.5): the Argument value is treated as Whitespace.

    -
    • -
  • -

    A Property (Section 3.4) key: the entire property, including both key and value, -is treated as Whitespace. A slashdash of just the property value is not allowed.

    -
    • -
  • -

    A Children Block (Section 3.6): the entire block, including all -children within, is treated as Whitespace. Only other children blocks, whether -slashdashed or not, may follow a slashdashed children block.

    -
    • -
-

A slashdash may be be followed by any amount of whitespace, including newlines and -comments (other than other slashdashes), before the element that it comments out.

-
-
-
-
-
-
-

-3.18. Newline -

-

The following character sequences should be treated as new -lines:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Table 3
AcronymNameCode Pt
CRLFCarriage Return and Line Feed - U+000D + U+000A -
CRCarriage Return - U+000D -
LFLine Feed - U+000A -
NELNext Line - U+0085 -
VTVertical tab - U+000B -
FFForm Feed - U+000C -
LSLine Separator - U+2028 -
PSParagraph Separator - U+2029 -
-

Note that for the purpose of new lines, the specific sequence CRLF is -considered a single newline.

-
-
-
-
-

-3.19. Disallowed Literal Code Points -

-

The following code points may not appear literally anywhere in the document. -They may be represented in Strings (but not Raw Strings) using Unicode Escapes (Section 3.11.1) (\u{...}, -except for non Unicode Scalar Value, which can't be represented even as escapes).

-
    -
  • -

    The codepoints U+0000-0008 or the codepoints U+000E-001F (various -control characters).

    -
    • -
  • -

    U+007F (the Delete control character).

    -
    • -
  • -

    Any codepoint that is not a Unicode Scalar -Value (U+D800-DFFF).

    -
    • -
  • -

    U+200E-200F, U+202A-202E, and U+2066-2069, the unicode -"direction control" -characters

    -
    • -
  • -

    U+FEFF, aka Zero-width Non-breaking Space (ZWNBSP)/Byte Order Mark (BOM), -except as the first code point in a document.

    -
    • -
-
-
-
-
-
-
-

-4. Full Grammar -

-

This is the full official grammar for KDL and should be considered -authoritative if something seems to disagree with the text above. The grammar -language syntax is defined in Section 4.1.

-
-
-document := bom? version? nodes
-
-// Nodes
-nodes := (line-space* node)* line-space*
-
-base-node := slashdash? type? node-space* string
-    (node-space+ slashdash? node-prop-or-arg)*
-    // slashdashed node-children must always be after props and args.
-    (node-space+ slashdash node-children)*
-    (node-space+ node-children)?
-    (node-space+ slashdash node-children)*
-    node-space*
-node := base-node node-terminator
-final-node := base-node node-terminator?
-
-// Entries
-node-prop-or-arg := prop | value
-node-children := '{' nodes final-node? '}'
-node-terminator := single-line-comment | newline | ';' | eof
-
-prop := string node-space* '=' node-space* value
-value := type? node-space* (string | number | keyword)
-type := '(' node-space* string node-space* ')'
-
-// Strings
-string := identifier-string | quoted-string | raw-string ¶
-
-identifier-string := unambiguous-ident | signed-ident | dotted-ident
-unambiguous-ident :=
-    ((identifier-char - digit - sign - '.') identifier-char*)
-    - disallowed-keyword-strings
-signed-ident :=
-    sign ((identifier-char - digit - '.') identifier-char*)?
-dotted-ident :=
-    sign? '.' ((identifier-char - digit) identifier-char*)?
-identifier-char :=
-    unicode - unicode-space - newline - [\\/(){};\[\]"#=]
-    - disallowed-literal-code-points
-disallowed-keyword-identifiers :=
-    'true' | 'false' | 'null' | 'inf' | '-inf' | 'nan'
-
-quoted-string :=
-    '"' single-line-string-body '"' |
-    '"""' newline
-    (multi-line-string-body newline)?
-    (unicode-space | ws-escape)* '"""'
-single-line-string-body := (string-character - newline)*
-multi-line-string-body := (('"' | '""')? string-character)*
-string-character :=
-    '\\' (["\\bfnrts] |
-    'u{' hex-unicode '}') |
-    ws-escape |
-    [^\\"] - disallowed-literal-code-points
-ws-escape := '\\' (unicode-space | newline)+
-hex-digit := [0-9a-fA-F]
-hex-unicode := hex-digit{1, 6} - surrogates
-surrogates := [dD][8-9a-fA-F]hex-digit{2}
-// U+D800-DFFF: D  8         00
-//              D  F         FF
-
-raw-string := '#' raw-string-quotes '#' | '#' raw-string '#'
-raw-string-quotes :=
-    '"' single-line-raw-string-body '"' |
-    '"""' newline
-    (multi-line-raw-string-body newline)?
-    unicode-space* '"""'
-single-line-raw-string-body :=
-    '' |
-    (single-line-raw-string-char - '"')
-        single-line-raw-string-char*? |
-    '"' (single-line-raw-string-char - '"')
-        single-line-raw-string-char*?
-single-line-raw-string-char :=
-    unicode - newline - disallowed-literal-code-points
-multi-line-raw-string-body :=
-    (unicode - disallowed-literal-code-points)*?
-
-// Numbers
-number := keyword-number | hex | octal | binary | decimal
-
-decimal := sign? integer ('.' integer)? exponent?
-exponent := ('e' | 'E') sign? integer
-integer := digit (digit | '_')*
-digit := [0-9]
-sign := '+' | '-'
-
-hex := sign? '0x' hex-digit (hex-digit | '_')*
-octal := sign? '0o' [0-7] [0-7_]*
-binary := sign? '0b' ('0' | '1') ('0' | '1' | '_')*
-
-// Keywords and booleans.
-keyword := boolean | '#null'
-keyword-number := '#inf' | '#-inf' | '#nan'
-boolean := '#true' | '#false'
-
-// Specific code points
-bom := '\u{FEFF}'
-disallowed-literal-code-points :=
-    See Table (Disallowed Literal Code Points)
-unicode := Any Unicode Scalar Value
-unicode-space := See Table
-    (All White_Space unicode characters which are not `newline`)
-
-// Comments
-single-line-comment := '//' ^newline* (newline | eof)
-multi-line-comment := '/*' commented-block
-commented-block :=
-    '*/' | (multi-line-comment | '*' | '/' | [^*/]+) commented-block
-slashdash := '/-' line-space*
-
-// Whitespace
-ws := unicode-space | multi-line-comment
-escline := '\\' ws* (single-line-comment | newline | eof)
-newline := See Table (All Newline White_Space)
-// Whitespace where newlines are allowed.
-line-space := node-space | newline | single-line-comment
-// Whitespace within nodes,
-// where newline-ish things must be esclined.
-node-space := ws* escline ws* | ws+
-
-// Version marker
-version :=
-    '/-' unicode-space* 'kdl-version' unicode-space+ ('1' | '2')
-    unicode-space* newline
-
-
-
-
-

-4.1. Grammar language -

-

The grammar language syntax is a combination of ABNF with some regex spice thrown in. -Specifically:

-
    -
  • -

    Single quotes (') are used to denote literal text. \ within a literal -string is used for escaping other single-quotes, for initiating unicode -characters using hex values (\u{FEFF}), and for escaping \ itself -(\\).

    -
    • -
  • -

    * is used for "zero or more", + is used for "one or more", and ? is -used for "zero or one". Per standard regex semantics, * and + are greedy; -they match as many instances as possible without failing the match.

    -
    • -
  • -

    *? (used only in raw strings) indicates a non-greedy match; -it matches as few instances as possible without failing the match.

    -
    • -
  • -

    is a cut point. It always matches and consumes no characters, -but once matched, the parser is not allowed to backtrack past that point in the source. -If a parser would rewind past the cut point, it must instead fail the overall parse, -as if it had run out of options. -(This is only used with the raw-string production, -to ensure the first instance of the appropriate closing quote sequence -is guaranteed to be the end of the raw string, -rather than allowing it to potentially consume more of the document unexpectedly.)

    -
    • -
  • -

    () can be used to group matches that must be matched together.

    -
    • -
  • -

    a | b means a or b, whichever matches first. If multiple items are before -a |, they are a single group. a b c | d is equivalent to (a b c) | d.

    -
    • -
  • -

    [] are used for regex-style character matches, where any character between -the brackets will be a single match. \ is used to escape \, [, and -]. They also support character ranges (0-9), and negation (^)

    -
    • -
  • -

    - is used for "except for" or "minus" whatever follows it. For example, -a - 'x' means "any a, except something that matches the literal 'x'".

    -
    • -
  • -

    The prefix ^ means "something that does not match" whatever follows it. -For example, ^foo means "must not match foo".

    -
    • -
  • -

    A single definition may be split over multiple lines. Newlines are treated as -spaces.

    -
    • -
  • -

    // followed by text on its own line is used as comment syntax.

    -
    • -
-
-
-
-
-
-
-

-Authors' Addresses -

-
-
Katerina Zoé Marchán Salvá
-
Microsoft
-
-
-
The KDL Contributors
-
-
-
- - - diff --git a/zkat/utf-8-must/draft-marchan-kdl2.txt b/zkat/utf-8-must/draft-marchan-kdl2.txt deleted file mode 100644 index f793744..0000000 --- a/zkat/utf-8-must/draft-marchan-kdl2.txt +++ /dev/null @@ -1,1241 +0,0 @@ - - - - -KDL Community K. Marchán - Microsoft - KDL Contributors - 20 January 2025 - - - The KDL Document Language - draft-marchan-kdl2-latest - -Abstract - - KDL is a node-oriented document language. Its niche and purpose - overlaps with XML, and as do many of its semantics. You can use KDL - both as a configuration language, and a data exchange or storage - format, if you so choose. - - This is the formal specification for KDL, including the intended data - model and the grammar. - - This document describes KDL version KDL 2.0.0. It was released on - 2024-12-21. It is the latest stable version of the language, and - will only be edited for minor copyedits or major errata. - -About This Document - - This note is to be removed before publishing as an RFC. - - Status information for this document may be found at - https://datatracker.ietf.org/doc/draft-marchan-kdl2/. - - information can be found at https://kdl.dev/. - - Source for this draft and an issue tracker can be found at - https://github.com/kdl-org/kdl. - -License - - This work is licensed under Creative Commons Attribution-ShareAlike - 4.0 International. To view a copy of this license, visit - https://creativecommons.org/licenses/by-sa/4.0/ - -Table of Contents - - 1. Compatibility - 2. Introduction - 3. Components - 3.1. Document - 3.1.1. Example - 3.2. Node - 3.2.1. Example - 3.3. Line Continuation - 3.3.1. Example - 3.4. Property - 3.5. Argument - 3.5.1. Example - 3.6. Children Block - 3.6.1. Example - 3.7. Value - 3.8. Type Annotation - 3.8.1. Reserved Type Annotations for Numbers Without Decimals: - 3.8.2. Reserved Type Annotations for Numbers With Decimals: - 3.8.3. Reserved Type Annotations for Strings: - 3.8.4. Examples - 3.9. String - 3.10. Identifier String - 3.10.1. Non-initial characters - 3.10.2. Non-identifier characters - 3.11. Quoted String - 3.11.1. Escapes - 3.12. Multi-line String - 3.12.1. Newline Normalization - 3.12.2. Examples - 3.12.3. Interaction with Whitespace Escapes - 3.13. Raw String - 3.13.1. Example - 3.14. Number - 3.14.1. Keyword Numbers - 3.15. Boolean - 3.15.1. Example - 3.16. Null - 3.16.1. Example - 3.17. Whitespace - 3.17.1. Single-line comments - 3.17.2. Multi-line comments - 3.17.3. Slashdash comments - 3.18. Newline - 3.19. Disallowed Literal Code Points - 4. Full Grammar - 4.1. Grammar language - Authors' Addresses - -1. Compatibility - - KDL 2.0 is designed such that for any given KDL document written as - KDL 1.0 (./SPEC_v1.md) or KDL 2.0, the parse will either fail - completely, or, if the parse succeeds, the data represented by a v1 - or v2 parser will be identical. This means that it's safe to use a - fallback parsing strategy in order to support both v1 and v2 - simultaneously. For example, node "foo" is a valid node in both - versions, and should be represented identically by parsers. - - A version marker /- kdl-version 2 (or 1) _MAY_ be added to the - beginning of a KDL document, optionally preceded by the BOM, and - parsers _MAY_ use that as a hint as to which version to parse the - document as. - -2. Introduction - - KDL is a node-oriented document language. Its niche and purpose - overlaps with XML, and as do many of its semantics. You can use KDL - both as a configuration language, and a data exchange or storage - format, if you so choose. - - The bulk of this document is dedicated to a long-form description of - all Components (Section 3) of a KDL document. There is also a much - more terse Grammar (Section 4) at the end of the document that covers - most of the rules, with some semantic exceptions involving the data - model. - - KDL is designed to be easy to read _and_ easy to implement. - - In this document, references to "left" or "right" refer to directions - in the _data stream_ towards the beginning or end, respectively; in - other words, the directions if the data stream were only ASCII text. - They do not refer to the writing direction of text, which can flow in - either direction, depending on the characters used. - -3. Components - -3.1. Document - - The toplevel concept of KDL is a Document. A Document is composed of - zero or more Nodes (Section 3.2), separated by newlines and - whitespace, and eventually terminated by an EOF. - - All KDL documents MUST be encoded in UTF-8 and conform to the - specifications in this document. - -3.1.1. Example - - The following is a document composed of two toplevel nodes: - - foo { - bar - } - baz - -3.2. Node - - Being a node-oriented language means that the real core component of - any KDL document is the "node". Every node must have a name, which - must be a String (Section 3.9). - - The name may be preceded by a Type Annotation (Section 3.8) to - further clarify its type, particularly in relation to its parent - node. (For example, clarifying that a particular date child node is - for the _publication_ date, rather than the last-modified date, with - (published)date.) - - Following the name are zero or more Arguments (Section 3.5) or - Properties (Section 3.4), separated by either whitespace - (Section 3.17) or a slash-escaped line continuation (Section 3.3). - Arguments and Properties may be interspersed in any order, much like - is common with positional arguments vs options in command line tools. - Collectively, Arguments and Properties may be referred to as - "Entries". - - Children (Section 3.6) can be placed after the name and the optional - Entries, possibly separated by either whitespace or a slash-escaped - line continuation. - - Arguments are ordered relative to each other and that order must be - preserved in order to maintain the semantics. Properties between - Arguments do not affect Argument ordering. - - By contrast, Properties _SHOULD NOT_ be assumed to be presented in a - given order. Children (Section 3.6) should be used if an order- - sensitive key/value data structure must be represented in KDL. Cf. - JSON objects preserving key order. - - Nodes _MAY_ be prefixed with Slashdash (Section 3.17.3) to "comment - out" the entire node, including its properties, arguments, and - children, and make it act as plain whitespace, even if it spreads - across multiple lines. - - Finally, a node is terminated by either a Newline (Section 3.18), a - semicolon (;), the end of a child block (}) or the end of the file/ - stream (an EOF). - -3.2.1. Example - - // `foo` will have an Argument value list like `[1, 3]`. - foo 1 key=val 3 { - bar - (role)baz 1 2 - } - -3.3. Line Continuation - - Line continuations allow Nodes (Section 3.2) to be spread across - multiple lines. - - A line continuation is a \ character followed by zero or more - whitespace items (including multiline comments) and an optional - single-line comment. It must be terminated by a Newline - (Section 3.18) (including the Newline that is part of single-line - comments). - - Following a line continuation, processing of a Node can continue as - usual. - -3.3.1. Example - - my-node 1 2 \ // comments are ok after \ - 3 4 // This is the actual end of the Node. - -3.4. Property - - A Property is a key/value pair attached to a Node (Section 3.2). A - Property is composed of a String (Section 3.9), followed immediately - by an equals sign (=, U+003D), and then a Value (Section 3.7). - - Properties should be interpreted left-to-right, with rightmost - properties with identical names overriding earlier properties. That - is: - - node a=1 a=2 - - In this example, the node's a value must be 2, not 1. - - No other guarantees about order should be expected by implementers. - Deserialized representations may iterate over properties in any order - and still be spec-compliant. - - Properties _MAY_ be prefixed with /- to "comment out" the entire - token and make it act as plain whitespace, even if it spreads across - multiple lines. - -3.5. Argument - - An Argument is a bare Value (Section 3.7) attached to a Node - (Section 3.2), with no associated key. It shares the same space as - Properties (Section 3.4), and may be interleaved with them. - - A Node may have any number of Arguments, which should be evaluated - left to right. KDL implementations _MUST_ preserve the order of - Arguments relative to each other (not counting Properties). - - Arguments _MAY_ be prefixed with /- to "comment out" the entire token - and make it act as plain whitespace, even if it spreads across - multiple lines. - -3.5.1. Example - - my-node 1 2 3 a b c - -3.6. Children Block - - A children block is a block of Nodes (Section 3.2), surrounded by { - and }. They are an optional part of nodes, and create a hierarchy of - KDL nodes. - - Regular node termination rules apply, which means multiple nodes can - be included in a single-line children block, as long as they're all - terminated by ;. - -3.6.1. Example - - parent { - child1 - child2 - } - - parent { child1; child2; } - -3.7. Value - - A value is either: a String (Section 3.9), a Number (Section 3.14), a - Boolean (Section 3.15), or Null (Section 3.16). - - Values _MUST_ be either Arguments (Section 3.5) or values of - Properties (Section 3.4). Only String (Section 3.9) values may be - used as Node (Section 3.2) names or Property (Section 3.4) keys. - - Values (both as arguments and in properties) _MAY_ be prefixed by a - single Type Annotation (Section 3.8). - -3.8. Type Annotation - - A type annotation is a prefix to any Node Name (Section 3.2) or Value - (Section 3.7) that includes a _suggestion_ of what type the value is - _intended_ to be treated as, or as a _context-specific elaboration_ - of the more generic type the node name indicates. - - Type annotations are written as a set of ( and ) with a single String - (Section 3.9) in it. It may contain Whitespace after the ( and - before the ), and may be separated from its target by Whitespace. - - KDL does not specify any restrictions on what implementations might - do with these annotations. They are free to ignore them, or use them - to make decisions about how to interpret a value. - - Additionally, the following type annotations MAY be recognized by KDL - parsers and, if used, SHOULD interpret these types as follows: - -3.8.1. Reserved Type Annotations for Numbers Without Decimals: - - Signed integers of various sizes (the number is the bit size): - - * i8 - - * i16 - - * i32 - - * i64 - - * i128 - - Unsigned integers of various sizes (the number is the bit size): - - * u8 - - * u16 - - * u32 - - * u64 - - * u128 - - Platform-dependent integer types, both signed and unsigned: - - * isize - - * usize - -3.8.2. Reserved Type Annotations for Numbers With Decimals: - - IEEE 754 floating point numbers, both single (32) and double (64) - precision: - - * f32 - - * f64 - - IEEE 754-2008 decimal floating point numbers - - * decimal64 - - * decimal128 - -3.8.3. Reserved Type Annotations for Strings: - - * date-time: ISO8601 date/time format. - - * time: "Time" section of ISO8601. - - * date: "Date" section of ISO8601. - - * duration: ISO8601 duration format. - - * decimal: IEEE 754-2008 decimal string format. - - * currency: ISO 4217 currency code. - - * country-2: ISO 3166-1 alpha-2 country code. - - * country-3: ISO 3166-1 alpha-3 country code. - - * country-subdivision: ISO 3166-2 country subdivision code. - - * email: RFC5322 email address. - - * idn-email: RFC6531 internationalized email address. - - * hostname: RFC1123 internet hostname (only ASCII segments) - - * idn-hostname: RFC5890 internationalized internet hostname (only xn - ---prefixed ASCII "punycode" segments, or non-ASCII segments) - - * ipv4: RFC2673 dotted-quad IPv4 address. - - * ipv6: RFC2373 IPv6 address. - - * url: RFC3986 URI. - - * url-reference: RFC3986 URI Reference. - - * irl: RFC3987 Internationalized Resource Identifier. - - * irl-reference: RFC3987 Internationalized Resource Identifier - Reference. - - * url-template: RFC6570 URI Template. - - * uuid: RFC4122 UUID. - - * regex: Regular expression. Specific patterns may be - implementation-dependent. - - * base64: A Base64-encoded string, denoting arbitrary binary data. - -3.8.4. Examples - - node (u8)123 - node prop=(regex).* - (published)date "1970-01-01" - (contributor)person name="Foo McBar" - -3.9. String - - Strings in KDL represent textual UTF-8 Values (Section 3.7). A - String is either an Identifier String (Section 3.10) (like foo), a - Quoted String (Section 3.11) (like "foo") or a Multi-Line String - (Section 3.12). Both Quoted and Multiline strings come in normal and - Raw String (Section 3.13) variants (like #"foo"#): - - * Identifier Strings let you write short, "single-word" strings with - a minimum of syntax - - * Quoted Strings let you write strings "like normal", with - whitespace and escapes. - - * Multi-Line Strings let you write strings across multiple lines and - with indentation that's not part of the string value. - - * Raw Strings don't allow any escapes, allowing you to not worry - about the string's content containing anything that might look - like an escape. - - Strings _MUST_ be represented as UTF-8 values. - - Strings _MUST NOT_ include the code points for disallowed literal - code points (Section 3.19) directly. Quoted and Multi-Line Strings - may include these code points as _values_ by representing them with - their corresponding \u{...} escape. - -3.10. Identifier String - - An Identifier String (sometimes referred to as just an "identifier") - is composed of any Unicode Scalar Value (https://unicode.org/ - glossary/#unicode_scalar_value) other than non-initial characters - (Section 3.10.1), followed by any number of Unicode Scalar Values - other than non-identifier characters (Section 3.10.2). - - A handful of patterns are disallowed, to avoid confusion with other - values: - - * idents that appear to start with a Number (Section 3.14) (like - 1.0v2 or -1em) or the "almost a number" pattern of a decimal point - without a leading digit (like .1). - - * idents that are the language keywords (inf, -inf, nan, true, - false, and null) without their leading #. - - Identifiers that match these patterns _MUST_ be treated as a syntax - error; such values can only be written as quoted or raw strings. The - precise details of the identifier syntax is specified in the Full - Grammar in Section 4. - -3.10.1. Non-initial characters - - The following characters cannot be the first character in an - Identifier String (Section 3.10): - - * Any decimal digit (0-9) - - * Any non-identifier characters (Section 3.10.2) - - Additionally, the following initial characters impose limitations on - subsequent characters: - - * the + and - characters can only be used as an initial character if - the second character is _not_ a digit. If the second character is - ., then the third character must _not_ be a digit. - - * the . character can only be used as an initial character if the - second character is _not_ a digit. - - This allows identifiers to look like --this or .md, and removes the - ambiguity of having an identifier look like a number. - -3.10.2. Non-identifier characters - - The following characters cannot be used anywhere in a Identifier - String (Section 3.10): - - * Any of (){}[]/\"#;= - - * Any Whitespace (Section 3.17) or Newline (Section 3.18). - - * Any disallowed literal code points (Section 3.19) in KDL - documents. - -3.11. Quoted String - - A Quoted String is delimited by " on either side of any number of - literal string characters except unescaped " and \. - - Literal Newline (Section 3.18) characters can only be included if - they are Escaped Whitespace (Section 3.11.1.1), which discards them - from the string value. Actually including a newline in the value - requires using a newline escape sequence, like \n, or using a Multi- - Line String (Section 3.12) which is actually designed for strings - stretching across multiple lines. - - Like Identifier Strings, Quoted Strings _MUST NOT_ include any of the - disallowed literal code-points (Section 3.19) as code points in their - body. - - Quoted Strings have a Raw String (Section 3.13) variant, which - disallows escapes. - -3.11.1. Escapes - - In addition to literal code points, a number of "escapes" are - supported in Quoted Strings. "Escapes" are the character \ followed - by another character, and are interpreted as described in the - following table: - - +==============+=========+=========================================+ - | Name | Escape | Code Pt | - +==============+=========+=========================================+ - | Line Feed | \n | U+000A | - +--------------+---------+-----------------------------------------+ - | Carriage | \r | U+000D | - | Return | | | - +--------------+---------+-----------------------------------------+ - | Character | \t | U+0009 | - | Tabulation | | | - | (Tab) | | | - +--------------+---------+-----------------------------------------+ - | Reverse | \\ | U+005C | - | Solidus | | | - | (Backslash) | | | - +--------------+---------+-----------------------------------------+ - | Quotation | \" | U+0022 | - | Mark (Double | | | - | Quote) | | | - +--------------+---------+-----------------------------------------+ - | Backspace | \b | U+0008 | - +--------------+---------+-----------------------------------------+ - | Form Feed | \f | U+000C | - +--------------+---------+-----------------------------------------+ - | Space | \s | U+0020 | - +--------------+---------+-----------------------------------------+ - | Unicode | \u{(1-6 | Code point described by hex characters, | - | Escape | hex | as long as it represents a Unicode | - | | chars)} | Scalar Value (https://unicode.org/ | - | | | glossary/#unicode_scalar_value) | - +--------------+---------+-----------------------------------------+ - | Whitespace | See | N/A | - | Escape | below | | - +--------------+---------+-----------------------------------------+ - - Table 1 - -3.11.1.1. Escaped Whitespace - - In addition to escaping individual characters, \ can also escape - whitespace. When a \ is followed by one or more literal whitespace - characters, the \ and all of that whitespace are discarded. For - example, - - "Hello World" - - and - - "Hello \ World" - - are semantically identical. See whitespace (Section 3.17) and - newlines (Section 3.18) for how whitespace is defined. - - Note that only literal whitespace is escaped; whitespace escapes (\n - and such) are retained. For example, these strings are all - semantically identical: - - "Hello\ \nWorld" - - "Hello\n\ - World" - - "Hello\nWorld" - - """ - Hello - World - """ - -3.11.1.2. Invalid escapes - - Except as described in the escapes table, above, \ _MUST NOT_ precede - any other characters in a string. - -3.12. Multi-line String - - Multi-Line Strings support multiple lines with literal, non-escaped - Newlines. They must use a special multi-line syntax, and they - automatically "dedent" the string, allowing its value to be indented - to a visually matching level as desired. - - A Multi-Line String is opened and closed by _three_ double-quote - characters, like """. Its first line _MUST_ immediately start with a - Newline (Section 3.18) after its opening """. Its final line _MUST_ - contain only whitespace before the closing """. All in-between lines - that contain non-newline, non-whitespace characters _MUST_ start with - _at least_ the exact same whitespace as the final line (precisely - matching codepoints, not merely counting characters or "size"); they - may contain additional whitespace following this prefix. The lines - in between may contain unescaped " (but no unescaped """ as this - would close the string). - - The value of the Multi-Line String omits the first and last Newline, - the Whitespace of the last line, and the matching Whitespace prefix - on all intermediate lines. The first and last Newline can be the - same character (that is, empty multi-line strings are legal). - - In other words, the final line specifies the whitespace prefix that - will be removed from all other lines. - - Multi-line Strings that do not immediately start with a Newline and - whose final """ is not preceeded by optional whitespace and a Newline - are illegal. This also means that """ may not be used for a single- - line String (e.g. """foo"""). - -3.12.1. Newline Normalization - - Literal Newline sequences in Multi-line Strings must be normalized to - a single U+000A (LF) during deserialization. This means, for - example, that CR LF becomes a single LF during parsing. - - This normalization does not apply to non-literal Newlines entered - using escape sequences. That is: - - multi-line """ - \r\n[CRLF] - foo[CRLF] - """ - - becomes: - - single-line "\r\n\nfoo" - - For clarity: this normalization applies to each individual Newline - sequence. That is, the literal sequence CRLF CRLF becomes LF LF, not - LF. - -3.12.2. Examples - -3.12.2.1. Indented multi-line string - - multi-line """ - foo - This is the base indentation - bar - """ - - This example's string value will be: - - foo - This is the base indentation - bar - - which is equivalent to - - " foo\nThis is the base indentation\n bar" - - when written as a single-line string. - -3.12.2.2. Shorter last-line indent - - If the last line wasn't indented as far, it won't dedent the rest of - the lines as much: - - multi-line """ - foo - This is no longer on the left edge - bar - """ - - This example's string value will be: - - foo - This is no longer on the left edge - bar - - Equivalent to - - " foo\n This is no longer on the left edge\n bar" - -3.12.2.3. Empty lines - - Empty lines can contain any whitespace, or none at all, and will be - reflected as empty in the value: - - multi-line """ - Indented a bit - - A second indented paragraph. - """ - - This example's string value will be: - - Indented a bit. - - A second indented paragraph. - - Equivalent to - - "Indented a bit.\n\nA second indented paragraph." - -3.12.2.4. Syntax errors - - The following yield *syntax errors*: - - multi-line """can't be single line""" - - multi-line """ - closing quote with non-whitespace prefix""" - - multi-line """stuff - """ - - // Every line must share the exact same prefix as the closing line. - multi-line """[\n] - [tab]a[\n] - [space][space]b[\n] - [space][tab][\n] - [tab]""" - -3.12.3. Interaction with Whitespace Escapes - - Multi-line strings support the same mechanism for escaping whitespace - as Quoted Strings. - - When processing a Multi-line String, implementations MUST dedent the - string _after_ resolving all whitespace escapes, but _before_ - resolving other backslash escapes. This means a whitespace escape - that attempts to escape the final line's newline and/or whitespace - prefix can be invalid: if removing escaped whitespace places the - closing """ on a line with non-whitespace characters, this escape is - invalid. - - For example, the following example is illegal: - - """ - foo - bar\ - """ - - // equivalent to - """ - foo - bar""" - - while the following example is allowed - - """ - foo \ - bar - baz - \ """ - - // equivalent to - """ - foo bar - baz - """ - -3.13. Raw String - - Both Quoted (Section 3.11) and Multi-Line Strings (Section 3.12) have - Raw String variants, which are identical in syntax except they do not - support \-escapes. This includes line-continuation escapes (\ + ws - collapsing to nothing). They otherwise share the same properties as - far as literal Newline (Section 3.18) characters go, multi-line - rules, and the requirement of UTF-8 representation. - - The Raw String variants are indicated by preceding the strings's - opening quotes with one or more # characters. The string is then - closed by its normal closing quotes, followed by a _matching_ number - of # characters. This means that the string may contain any - combination of " and # characters other than its closing delimiter - (e.g., if a raw string starts with ##", it can contain " or "#, but - not "## or "###). - - Like other Strings, Raw Strings _MUST NOT_ include any of the - disallowed literal code-points (Section 3.19) as code points in their - body. Unlike with Quoted Strings, these cannot simply be escaped, - and are thus unrepresentable when using Raw Strings. - -3.13.1. Example - - just-escapes #"\n will be literal"# - - The string contains the literal characters \n will be literal. - - quotes-and-escapes ##"hello\n\r\asd"#world"## - - The string contains the literal characters hello\n\r\asd"#world - - raw-multi-line #""" - Here's a """ - multiline string - """ - without escapes. - """# - - The string contains the value - - Here's a """ - multiline string - """ - without escapes. - - or equivalently, - - "Here's a \"\"\"\n multiline string\n \"\"\"\nwithout escapes." - - as a Quoted String. - -3.14. Number - - Numbers in KDL represent numerical Values (Section 3.7). There is no - logical distinction in KDL between real numbers, integers, and - floating point numbers. It's up to individual implementations to - determine how to represent KDL numbers. - - There are five syntaxes for Numbers: Keywords, Decimal, Hexadecimal, - Octal, and Binary. - - * All non-Keyword (Section 3.14.1) numbers may optionally start with - one of - or +, which determine whether they'll be positive or - negative. - - * Binary numbers start with 0b and only allow 0 and 1 as digits, - which may be separated by _. They represent numbers in radix 2. - - * Octal numbers start with 0o and only allow digits between 0 and 7, - which may be separated by _. They represent numbers in radix 8. - - * Hexadecimal numbers start with 0x and allow digits between 0 and - 9, as well as letters A through F, in either lower or upper case, - which may be separated by _. They represent numbers in radix 16. - - * Decimal numbers are a bit more special: - - - They have no radix prefix. - - - They use digits 0 through 9, which may be separated by _. - - - They may optionally include a decimal separator ., followed by - more digits, which may again be separated by _. - - - They may optionally be followed by E or e, an optional - or +, - and more digits, to represent an exponent value. - - Note that, similar to JSON and some other languages, numbers without - an integer digit (such as .1) are illegal. They must be written with - at least one integer digit, like 0.1. (These patterns are also - disallowed from Identifier Strings (Section 3.10), to avoid - confusion.) - -3.14.1. Keyword Numbers - - There are three special "keyword" numbers included in KDL to - accomodate the widespread use of IEEE 754 - (https://en.wikipedia.org/wiki/IEEE_754) floats: - - * #inf - floating point positive infinity. - - * #-inf - floating point negative infinity. - - * #nan - floating point NaN/Not a Number. - - To go along with this and prevent foot guns, the bare Identifier - Strings (Section 3.10) inf, -inf, and nan are considered illegal - identifiers and should yield a syntax error. - - The existence of these keywords does not imply that any numbers be - represented as IEEE 754 floats. These are simply for clarity and - convenience for any implementation that chooses to represent their - numbers in this way. - -3.15. Boolean - - A boolean Value (Section 3.7) is either the symbol #true or #false. - These _SHOULD_ be represented by implementation as boolean logical - values, or some approximation thereof. - -3.15.1. Example - - my-node #true value=#false - -3.16. Null - - The symbol #null represents a null Value (Section 3.7). It's up to - the implementation to decide how to represent this, but it generally - signals the "absence" of a value. - -3.16.1. Example - - my-node #null key=#null - -3.17. Whitespace - - The following characters should be treated as non-Newline - (Section 3.18) white space - (https://www.unicode.org/Public/UCD/latest/ucd/PropList.txt): - - +===========================+=========+ - | Name | Code Pt | - +===========================+=========+ - | Character Tabulation | U+0009 | - +---------------------------+---------+ - | Space | U+0020 | - +---------------------------+---------+ - | No-Break Space | U+00A0 | - +---------------------------+---------+ - | Ogham Space Mark | U+1680 | - +---------------------------+---------+ - | En Quad | U+2000 | - +---------------------------+---------+ - | Em Quad | U+2001 | - +---------------------------+---------+ - | En Space | U+2002 | - +---------------------------+---------+ - | Em Space | U+2003 | - +---------------------------+---------+ - | Three-Per-Em Space | U+2004 | - +---------------------------+---------+ - | Four-Per-Em Space | U+2005 | - +---------------------------+---------+ - | Six-Per-Em Space | U+2006 | - +---------------------------+---------+ - | Figure Space | U+2007 | - +---------------------------+---------+ - | Punctuation Space | U+2008 | - +---------------------------+---------+ - | Thin Space | U+2009 | - +---------------------------+---------+ - | Hair Space | U+200A | - +---------------------------+---------+ - | Narrow No-Break Space | U+202F | - +---------------------------+---------+ - | Medium Mathematical Space | U+205F | - +---------------------------+---------+ - | Ideographic Space | U+3000 | - +---------------------------+---------+ - - Table 2 - -3.17.1. Single-line comments - - Any text after //, until the next literal Newline (Section 3.18) is - "commented out", and is considered to be Whitespace (Section 3.17). - -3.17.2. Multi-line comments - - In addition to single-line comments using //, comments can also be - started with /* and ended with */. These comments can span multiple - lines. They are allowed in all positions where Whitespace - (Section 3.17) is allowed and can be nested. - -3.17.3. Slashdash comments - - Finally, a special kind of comment called a "slashdash", denoted by - /-, can be used to comment out entire _components_ of a KDL document - logically, and have those elements not be included as part of the - parsed document data. - - Slashdash comments can be used before the following, including before - their type annotations, if present: - - * A Node (Section 3.2): the entire Node is treated as Whitespace, - including all props, args, and children. - - * An Argument (Section 3.5): the Argument value is treated as - Whitespace. - - * A Property (Section 3.4) key: the entire property, including both - key and value, is treated as Whitespace. A slashdash of just the - property value is not allowed. - - * A Children Block (Section 3.6): the entire block, including all - children within, is treated as Whitespace. Only other children - blocks, whether slashdashed or not, may follow a slashdashed - children block. - - A slashdash may be be followed by any amount of whitespace, including - newlines and comments (other than other slashdashes), before the - element that it comments out. - -3.18. Newline - - The following character sequences should be treated as new lines - (https://www.unicode.org/versions/Unicode16.0.0/core-spec/chapter- - 5/#G41643): - - +=========+===============================+=================+ - | Acronym | Name | Code Pt | - +=========+===============================+=================+ - | CRLF | Carriage Return and Line Feed | U+000D + U+000A | - +---------+-------------------------------+-----------------+ - | CR | Carriage Return | U+000D | - +---------+-------------------------------+-----------------+ - | LF | Line Feed | U+000A | - +---------+-------------------------------+-----------------+ - | NEL | Next Line | U+0085 | - +---------+-------------------------------+-----------------+ - | VT | Vertical tab | U+000B | - +---------+-------------------------------+-----------------+ - | FF | Form Feed | U+000C | - +---------+-------------------------------+-----------------+ - | LS | Line Separator | U+2028 | - +---------+-------------------------------+-----------------+ - | PS | Paragraph Separator | U+2029 | - +---------+-------------------------------+-----------------+ - - Table 3 - - Note that for the purpose of new lines, the specific sequence CRLF is - considered _a single newline_. - -3.19. Disallowed Literal Code Points - - The following code points may not appear literally anywhere in the - document. They may be represented in Strings (but not Raw Strings) - using Unicode Escapes (Section 3.11.1) (\u{...}, except for non - Unicode Scalar Value, which can't be represented even as escapes). - - * The codepoints U+0000-0008 or the codepoints U+000E-001F (various - control characters). - - * U+007F (the Delete control character). - - * Any codepoint that is not a Unicode Scalar Value - (https://unicode.org/glossary/#unicode_scalar_value) - (U+D800-DFFF). - - * U+200E-200F, U+202A-202E, and U+2066-2069, the unicode "direction - control" characters (https://www.w3.org/International/questions/ - qa-bidi-unicode-controls) - - * U+FEFF, aka Zero-width Non-breaking Space (ZWNBSP)/Byte Order Mark - (BOM), except as the first code point in a document. - -4. Full Grammar - - This is the full official grammar for KDL and should be considered - authoritative if something seems to disagree with the text above. - The grammar language syntax is defined in Section 4.1. - - document := bom? version? nodes - - // Nodes - nodes := (line-space* node)* line-space* - - base-node := slashdash? type? node-space* string - (node-space+ slashdash? node-prop-or-arg)* - // slashdashed node-children must always be after props and args. - (node-space+ slashdash node-children)* - (node-space+ node-children)? - (node-space+ slashdash node-children)* - node-space* - node := base-node node-terminator - final-node := base-node node-terminator? - - // Entries - node-prop-or-arg := prop | value - node-children := '{' nodes final-node? '}' - node-terminator := single-line-comment | newline | ';' | eof - - prop := string node-space* '=' node-space* value - value := type? node-space* (string | number | keyword) - type := '(' node-space* string node-space* ')' - - // Strings - string := identifier-string | quoted-string | raw-string ¶ - - identifier-string := unambiguous-ident | signed-ident | dotted-ident - unambiguous-ident := - ((identifier-char - digit - sign - '.') identifier-char*) - - disallowed-keyword-strings - signed-ident := - sign ((identifier-char - digit - '.') identifier-char*)? - dotted-ident := - sign? '.' ((identifier-char - digit) identifier-char*)? - identifier-char := - unicode - unicode-space - newline - [\\/(){};\[\]"#=] - - disallowed-literal-code-points - disallowed-keyword-identifiers := - 'true' | 'false' | 'null' | 'inf' | '-inf' | 'nan' - - quoted-string := - '"' single-line-string-body '"' | - '"""' newline - (multi-line-string-body newline)? - (unicode-space | ws-escape)* '"""' - single-line-string-body := (string-character - newline)* - multi-line-string-body := (('"' | '""')? string-character)* - string-character := - '\\' (["\\bfnrts] | - 'u{' hex-unicode '}') | - ws-escape | - [^\\"] - disallowed-literal-code-points - ws-escape := '\\' (unicode-space | newline)+ - hex-digit := [0-9a-fA-F] - hex-unicode := hex-digit{1, 6} - surrogates - surrogates := [dD][8-9a-fA-F]hex-digit{2} - // U+D800-DFFF: D 8 00 - // D F FF - - raw-string := '#' raw-string-quotes '#' | '#' raw-string '#' - raw-string-quotes := - '"' single-line-raw-string-body '"' | - '"""' newline - (multi-line-raw-string-body newline)? - unicode-space* '"""' - single-line-raw-string-body := - '' | - (single-line-raw-string-char - '"') - single-line-raw-string-char*? | - '"' (single-line-raw-string-char - '"') - single-line-raw-string-char*? - single-line-raw-string-char := - unicode - newline - disallowed-literal-code-points - multi-line-raw-string-body := - (unicode - disallowed-literal-code-points)*? - - // Numbers - number := keyword-number | hex | octal | binary | decimal - - decimal := sign? integer ('.' integer)? exponent? - exponent := ('e' | 'E') sign? integer - integer := digit (digit | '_')* - digit := [0-9] - sign := '+' | '-' - - hex := sign? '0x' hex-digit (hex-digit | '_')* - octal := sign? '0o' [0-7] [0-7_]* - binary := sign? '0b' ('0' | '1') ('0' | '1' | '_')* - - // Keywords and booleans. - keyword := boolean | '#null' - keyword-number := '#inf' | '#-inf' | '#nan' - boolean := '#true' | '#false' - - // Specific code points - bom := '\u{FEFF}' - disallowed-literal-code-points := - See Table (Disallowed Literal Code Points) - unicode := Any Unicode Scalar Value - unicode-space := See Table - (All White_Space unicode characters which are not `newline`) - - // Comments - single-line-comment := '//' ^newline* (newline | eof) - multi-line-comment := '/*' commented-block - commented-block := - '*/' | (multi-line-comment | '*' | '/' | [^*/]+) commented-block - slashdash := '/-' line-space* - - // Whitespace - ws := unicode-space | multi-line-comment - escline := '\\' ws* (single-line-comment | newline | eof) - newline := See Table (All Newline White_Space) - // Whitespace where newlines are allowed. - line-space := node-space | newline | single-line-comment - // Whitespace within nodes, - // where newline-ish things must be esclined. - node-space := ws* escline ws* | ws+ - - // Version marker - version := - '/-' unicode-space* 'kdl-version' unicode-space+ ('1' | '2') - unicode-space* newline - -4.1. Grammar language - - The grammar language syntax is a combination of ABNF with some regex - spice thrown in. Specifically: - - * Single quotes (') are used to denote literal text. \ within a - literal string is used for escaping other single-quotes, for - initiating unicode characters using hex values (\u{FEFF}), and for - escaping \ itself (\\). - - * * is used for "zero or more", + is used for "one or more", and ? - is used for "zero or one". Per standard regex semantics, * and + - are _greedy_; they match as many instances as possible without - failing the match. - - * *? (used only in raw strings) indicates a _non-greedy_ match; it - matches as _few_ instances as possible without failing the match. - - * ¶ is a _cut point_. It always matches and consumes no characters, - but once matched, the parser is not allowed to backtrack past that - point in the source. If a parser would rewind past the cut point, - it must instead fail the overall parse, as if it had run out of - options. (This is only used with the raw-string production, to - ensure the first instance of the appropriate closing quote - sequence is guaranteed to be the end of the raw string, rather - than allowing it to potentially consume more of the document - unexpectedly.) - - * () can be used to group matches that must be matched together. - - * a | b means a or b, whichever matches first. If multiple items - are before a |, they are a single group. a b c | d is equivalent - to (a b c) | d. - - * [] are used for regex-style character matches, where any character - between the brackets will be a single match. \ is used to escape - \, [, and ]. They also support character ranges (0-9), and - negation (^) - - * - is used for "except for" or "minus" whatever follows it. For - example, a - 'x' means "any a, except something that matches the - literal 'x'". - - * The prefix ^ means "something that does not match" whatever - follows it. For example, ^foo means "must not match foo". - - * A single definition may be split over multiple lines. Newlines - are treated as spaces. - - * // followed by text on its own line is used as comment syntax. - -Authors' Addresses - - Katerina Zoé Marchán Salvá - Microsoft - - - The KDL Contributors diff --git a/zkat/utf-8-must/index.html b/zkat/utf-8-must/index.html deleted file mode 100644 index 454a230..0000000 --- a/zkat/utf-8-must/index.html +++ /dev/null @@ -1,45 +0,0 @@ - - - - kdl-org/kdl zkat/utf-8-must preview - - - - -

Editor's drafts for zkat/utf-8-must branch of kdl-org/kdl

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KDLplain textsame as main
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