mirror of https://codeberg.org/pzp/pzp-set.git
140 lines
2.5 KiB
Markdown
140 lines
2.5 KiB
Markdown
## Feed tangle
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(Lipmaa backlinks are not shown in the diagram below, but they should exist)
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```mermaid
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graph RL
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R["(Feed root)"]
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A[adds alice]
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B[adds bob]
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C[deletes alices]
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D[adds bob]
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E[adds carol]
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C-->B-->A-->R
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D--->A
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E-->D & C
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classDef default fill:#bbb,stroke:#fff0,color:#000
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```
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Reducing the tangle above in a topological sort allows you to build an array
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(a JSON object) `[bob, carol]`.
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## Msg type
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`msg.metadata.type` MUST start with `set_v1__`. E.g. `set_v1__follows`.
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## Msg content
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`msg.content` format:
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```typescript
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interface MsgContent {
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add: Array<string>,
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del: Array<string>,
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supersedes: Array<MsgHash>,
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}
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```
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## Supersedes links
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When you add or delete an item in a set, in the `supersedes` array you MUST
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point to the currently-known highest-depth msg that added or deleted that item.
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Also, when you *add any item*, in the `supersedes` array you SHOULD point to
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all currently-known highest-depth msgs that *deleted something*.
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The set of *not-transitively-superseded-by-anyone* msgs comprise the
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"item roots" of the record. To allow pruning the tangle, we can delete
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(or, if we want to keep metadata, "erase") all msgs preceding the item roots.
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Suppose the tangle is grown in the order below, then the field roots are
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highlighted in blue.
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```mermaid
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graph RL
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R["(Feed root)"]
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A[adds alice]:::blue
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A-->R
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classDef default fill:#bbb,stroke:#fff0,color:#000
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classDef blue fill:#6af,stroke:#fff0,color:#000
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```
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-----
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```mermaid
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graph RL
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R["(Feed root)"]
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A[adds alice]:::blue
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B[adds bob]:::blue
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B-->A-->R
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classDef default fill:#bbb,stroke:#fff0,color:#000
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classDef blue fill:#6af,stroke:#fff0,color:#000
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```
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-----
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```mermaid
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graph RL
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R["(Feed root)"]
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A[adds alice]
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B[adds bob]:::blue
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C[deletes alices]:::blue
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C-->B-->A-->R
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C-- supersedes -->A
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linkStyle 3 stroke-width:1px,stroke:#05f
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classDef default fill:#bbb,stroke:#fff0,color:#000
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classDef blue fill:#6af,stroke:#fff0,color:#000
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```
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-----
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```mermaid
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graph RL
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R["(Feed root)"]
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A[adds alice]
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B[adds bob]:::blue
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C[deletes alices]:::blue
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D[adds bob]:::blue
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C-->B-->A-->R
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C-- supersedes -->A
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D--->A
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linkStyle 3 stroke-width:1px,stroke:#05f
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classDef default fill:#bbb,stroke:#fff0,color:#000
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classDef blue fill:#6af,stroke:#fff0,color:#000
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```
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-----
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```mermaid
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graph RL
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R["(Feed root)"]
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A[adds alice]
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B[adds bob]:::blue
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C[deletes alices]
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D[adds bob]:::blue
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E[adds carol]:::blue
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C-->B-->A-->R
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C-- supersedes -->A
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D--->A
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E-->D & C
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E-- supersedes -->C
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linkStyle 3,7 stroke-width:1px,stroke:#05f
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classDef default fill:#bbb,stroke:#fff0,color:#000
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classDef blue fill:#6af,stroke:#fff0,color:#000
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```
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