diff --git a/src/autorouter/autorouter.rs b/src/autorouter/autorouter.rs
index 0d208f1..5f38575 100644
--- a/src/autorouter/autorouter.rs
+++ b/src/autorouter/autorouter.rs
@@ -17,11 +17,10 @@ use crate::{
         ratsnest::{Ratsnest, RatvertexIndex},
         selection::Selection,
     },
-    board::Board,
+    board::{mesadata::MesadataTrait, Board},
     drawing::{
         dot::FixedDotIndex,
         graph::{GetLayer, GetMaybeNet},
-        rules::RulesTrait,
     },
     layout::Layout,
     router::{
@@ -55,7 +54,7 @@ pub struct Autoroute {
 impl Autoroute {
     pub fn new(
         ratlines: impl IntoIterator<Item = EdgeIndex<usize>> + 'static,
-        autorouter: &mut Autorouter<impl RulesTrait>,
+        autorouter: &mut Autorouter<impl MesadataTrait>,
     ) -> Result<Self, AutorouterError> {
         let mut ratlines_iter = Box::new(ratlines.into_iter());
 
@@ -75,10 +74,10 @@ impl Autoroute {
         Ok(this)
     }
 
-    pub fn step<R: RulesTrait>(
+    pub fn step<M: MesadataTrait>(
         &mut self,
-        autorouter: &mut Autorouter<R>,
-        observer: &mut impl RouterObserverTrait<R>,
+        autorouter: &mut Autorouter<M>,
+        observer: &mut impl RouterObserverTrait<M>,
     ) -> Result<AutorouterStatus, AutorouterError> {
         let (new_navmesh, new_ratline) = if let Some(cur_ratline) = self.ratlines_iter.next() {
             let (source, target) = autorouter.ratline_endpoints(cur_ratline);
@@ -121,13 +120,13 @@ impl Autoroute {
     }
 }
 
-pub struct Autorouter<R: RulesTrait> {
-    board: Board<R>,
+pub struct Autorouter<M: MesadataTrait> {
+    board: Board<M>,
     ratsnest: Ratsnest,
 }
 
-impl<R: RulesTrait> Autorouter<R> {
-    pub fn new(board: Board<R>) -> Result<Self, InsertionError> {
+impl<M: MesadataTrait> Autorouter<M> {
+    pub fn new(board: Board<M>) -> Result<Self, InsertionError> {
         let ratsnest = Ratsnest::new(board.layout())?;
         Ok(Self { board, ratsnest })
     }
@@ -135,7 +134,7 @@ impl<R: RulesTrait> Autorouter<R> {
     pub fn autoroute(
         &mut self,
         selection: &Selection,
-        observer: &mut impl RouterObserverTrait<R>,
+        observer: &mut impl RouterObserverTrait<M>,
     ) -> Result<(), AutorouterError> {
         let mut autoroute = self.autoroute_walk(selection)?;
 
@@ -225,7 +224,7 @@ impl<R: RulesTrait> Autorouter<R> {
             .collect()
     }
 
-    pub fn board(&self) -> &Board<R> {
+    pub fn board(&self) -> &Board<M> {
         &self.board
     }
 
diff --git a/src/autorouter/invoker.rs b/src/autorouter/invoker.rs
index c747869..511dfcf 100644
--- a/src/autorouter/invoker.rs
+++ b/src/autorouter/invoker.rs
@@ -7,7 +7,7 @@ use crate::{
         selection::Selection,
         Autoroute, Autorouter, AutorouterError, AutorouterStatus,
     },
-    drawing::rules::RulesTrait,
+    board::mesadata::MesadataTrait,
     layout::Layout,
     router::{EmptyRouterObserver, RouterObserverTrait},
 };
@@ -35,10 +35,10 @@ pub enum Execute {
 }
 
 impl Execute {
-    pub fn step<R: RulesTrait>(
+    pub fn step<M: MesadataTrait>(
         &mut self,
-        invoker: &mut Invoker<R>,
-        observer: &mut impl RouterObserverTrait<R>,
+        invoker: &mut Invoker<M>,
+        observer: &mut impl RouterObserverTrait<M>,
     ) -> Result<InvokerStatus, InvokerError> {
         match self {
             Execute::Autoroute(autoroute) => {
@@ -51,31 +51,31 @@ impl Execute {
     }
 }
 
-pub struct Invoker<R: RulesTrait> {
-    autorouter: Autorouter<R>,
+pub struct Invoker<M: MesadataTrait> {
+    autorouter: Autorouter<M>,
     history: History,
 }
 
-impl<R: RulesTrait> Invoker<R> {
-    pub fn new(autorouter: Autorouter<R>) -> Self {
+impl<M: MesadataTrait> Invoker<M> {
+    pub fn new(autorouter: Autorouter<M>) -> Self {
         Self::new_with_history(autorouter, History::new())
     }
 
-    pub fn new_with_history(autorouter: Autorouter<R>, history: History) -> Self {
+    pub fn new_with_history(autorouter: Autorouter<M>, history: History) -> Self {
         Self {
             autorouter,
             history,
         }
     }
 
-    pub fn destruct(self) -> (Autorouter<R>, History) {
+    pub fn destruct(self) -> (Autorouter<M>, History) {
         (self.autorouter, self.history)
     }
 
     pub fn execute(
         &mut self,
         command: Command,
-        observer: &mut impl RouterObserverTrait<R>,
+        observer: &mut impl RouterObserverTrait<M>,
     ) -> Result<(), InvokerError> {
         let mut execute = self.execute_walk(command);
 
@@ -142,7 +142,7 @@ impl<R: RulesTrait> Invoker<R> {
         self.history.set_undone(undone.into_iter());
     }
 
-    pub fn autorouter(&self) -> &Autorouter<R> {
+    pub fn autorouter(&self) -> &Autorouter<M> {
         &self.autorouter
     }
 
diff --git a/src/autorouter/selection.rs b/src/autorouter/selection.rs
index 6f19ba1..45abf73 100644
--- a/src/autorouter/selection.rs
+++ b/src/autorouter/selection.rs
@@ -3,11 +3,8 @@ use std::collections::HashSet;
 use serde::{Deserialize, Serialize};
 
 use crate::{
-    board::Board,
-    drawing::{
-        graph::{GetLayer, MakePrimitive, PrimitiveIndex},
-        rules::RulesTrait,
-    },
+    board::{mesadata::MesadataTrait, Board},
+    drawing::graph::{GetLayer, MakePrimitive, PrimitiveIndex},
     graph::GenericIndex,
     layout::NodeIndex,
 };
@@ -30,7 +27,7 @@ impl Selection {
         }
     }
 
-    pub fn toggle_at_node(&mut self, board: &Board<impl RulesTrait>, node: NodeIndex) {
+    pub fn toggle_at_node(&mut self, board: &Board<impl MesadataTrait>, node: NodeIndex) {
         let Some(selector) = self.node_selector(board, node) else {
             return;
         };
@@ -42,15 +39,15 @@ impl Selection {
         }
     }
 
-    fn select(&mut self, board: &Board<impl RulesTrait>, selector: Selector) {
+    fn select(&mut self, board: &Board<impl MesadataTrait>, selector: Selector) {
         self.selectors.insert(selector);
     }
 
-    fn deselect(&mut self, board: &Board<impl RulesTrait>, selector: &Selector) {
+    fn deselect(&mut self, board: &Board<impl MesadataTrait>, selector: &Selector) {
         self.selectors.remove(selector);
     }
 
-    pub fn contains_node(&self, board: &Board<impl RulesTrait>, node: NodeIndex) -> bool {
+    pub fn contains_node(&self, board: &Board<impl MesadataTrait>, node: NodeIndex) -> bool {
         let Some(selector) = self.node_selector(board, node) else {
             return false;
         };
@@ -58,7 +55,11 @@ impl Selection {
         self.selectors.contains(&selector)
     }
 
-    fn node_selector(&self, board: &Board<impl RulesTrait>, node: NodeIndex) -> Option<Selector> {
+    fn node_selector(
+        &self,
+        board: &Board<impl MesadataTrait>,
+        node: NodeIndex,
+    ) -> Option<Selector> {
         let layer = match node {
             NodeIndex::Primitive(primitive) => {
                 primitive.primitive(board.layout().drawing()).layer()
diff --git a/src/bin/topola-egui/app.rs b/src/bin/topola-egui/app.rs
index 68ad320..16f1c3f 100644
--- a/src/bin/topola-egui/app.rs
+++ b/src/bin/topola-egui/app.rs
@@ -22,7 +22,7 @@ use topola::{
         rules::RulesTrait,
         Drawing, Infringement, LayoutException,
     },
-    dsn::{design::DsnDesign, rules::DsnRules},
+    dsn::{design::DsnDesign, mesadata::DsnMesadata},
     geometry::{
         compound::CompoundManagerTrait,
         primitive::{BendShape, DotShape, PrimitiveShape, PrimitiveShapeTrait, SegShape},
@@ -59,7 +59,7 @@ pub struct App {
     overlay: Option<Overlay>,
 
     #[serde(skip)]
-    invoker: Option<Arc<Mutex<Invoker<DsnRules>>>>,
+    invoker: Option<Arc<Mutex<Invoker<DsnMesadata>>>>,
 
     #[serde(skip)]
     shared_data: Arc<Mutex<SharedData>>,
diff --git a/src/bin/topola-sdl2-demo/main.rs b/src/bin/topola-sdl2-demo/main.rs
index e7b1464..6a4d9e6 100644
--- a/src/bin/topola-sdl2-demo/main.rs
+++ b/src/bin/topola-sdl2-demo/main.rs
@@ -21,7 +21,7 @@ use topola::drawing::rules::{Conditions, RulesTrait};
 use topola::drawing::seg::FixedSegWeight;
 use topola::drawing::{Infringement, LayoutException};
 use topola::dsn::design::DsnDesign;
-use topola::dsn::rules::DsnRules;
+use topola::dsn::mesadata::DsnMesadata;
 use topola::geometry::primitive::{PrimitiveShape, PrimitiveShapeTrait};
 use topola::geometry::shape::ShapeTrait;
 use topola::layout::zone::MakePolyShape;
diff --git a/src/board/board.rs b/src/board/board.rs
index b4aacef..87b095c 100644
--- a/src/board/board.rs
+++ b/src/board/board.rs
@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 
 use crate::{
+    board::mesadata::MesadataTrait,
     drawing::{
         band::BandIndex,
         dot::{FixedDotIndex, FixedDotWeight},
@@ -20,16 +21,16 @@ use crate::{
 };
 
 #[derive(Debug)]
-pub struct Board<R: RulesTrait> {
-    layout: Layout<R>,
+pub struct Board<M: MesadataTrait> {
+    layout: Layout<M>,
     node_to_pinname: HashMap<NodeIndex, String>,
     layer_to_layername: HashMap<u64, String>,
     net_to_netname: HashMap<usize, String>,
     pinname_pair_to_band: HashMap<(String, String), BandIndex>,
 }
 
-impl<R: RulesTrait> Board<R> {
-    pub fn new(layout: Layout<R>) -> Self {
+impl<M: MesadataTrait> Board<M> {
+    pub fn new(layout: Layout<M>) -> Self {
         Self {
             layout,
             node_to_pinname: HashMap::new(),
@@ -122,7 +123,7 @@ impl<R: RulesTrait> Board<R> {
         &mut self,
         navmesh: Navmesh,
         width: f64,
-        observer: &mut impl RouterObserverTrait<R>,
+        observer: &mut impl RouterObserverTrait<M>,
     ) -> Result<BandIndex, RouterError> {
         let source_pinname = self
             .node_pinname(GenericNode::Primitive(navmesh.source().into()))
@@ -199,11 +200,11 @@ impl<R: RulesTrait> Board<R> {
         }
     }
 
-    pub fn layout(&self) -> &Layout<R> {
+    pub fn layout(&self) -> &Layout<M> {
         &self.layout
     }
 
-    pub fn layout_mut(&mut self) -> &mut Layout<R> {
+    pub fn layout_mut(&mut self) -> &mut Layout<M> {
         &mut self.layout
     }
 }
diff --git a/src/board/mesadata.rs b/src/board/mesadata.rs
new file mode 100644
index 0000000..cdbf113
--- /dev/null
+++ b/src/board/mesadata.rs
@@ -0,0 +1,10 @@
+use crate::{drawing::rules::RulesTrait, layout::NodeIndex};
+
+// TODO: use this trait.
+pub trait MesadataTrait: RulesTrait {
+    /*fn node_pinname(&self, node: NodeIndex);
+    fn layer_layername(&self, layer: u64) -> &str;
+    fn layername_layer(&self, layername: &str) -> u64;
+    fn net_netname(&self, net: usize) -> &str;
+    fn netname_net(&self, netname: &str) -> usize;*/
+}
diff --git a/src/board/mod.rs b/src/board/mod.rs
index 928e4c1..34c3a1d 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -1,3 +1,4 @@
 mod board;
+pub mod mesadata;
 
 pub use board::*;
diff --git a/src/dsn/design.rs b/src/dsn/design.rs
index 4c030dc..1610ed7 100644
--- a/src/dsn/design.rs
+++ b/src/dsn/design.rs
@@ -8,7 +8,7 @@ use crate::{
     drawing::{dot::FixedDotWeight, seg::FixedSegWeight, Drawing},
     dsn::{
         de,
-        rules::DsnRules,
+        mesadata::DsnMesadata,
         structure::{self, DsnFile, Layer, Pcb, Shape},
     },
     geometry::compound::CompoundManagerTrait,
@@ -44,8 +44,8 @@ impl DsnDesign {
         Ok(Self { pcb })
     }
 
-    pub fn make_board(&self) -> Board<DsnRules> {
-        let rules = DsnRules::from_pcb(&self.pcb);
+    pub fn make_board(&self) -> Board<DsnMesadata> {
+        let rules = DsnMesadata::from_pcb(&self.pcb);
         let mut board = Board::new(Layout::new(Drawing::new(rules)));
 
         // mapping of pin -> net prepared for adding pins
@@ -341,7 +341,7 @@ impl DsnDesign {
     }
 
     fn layer(
-        board: &Board<DsnRules>,
+        board: &Board<DsnMesadata>,
         layer_vec: &Vec<Layer>,
         layer_name: &str,
         front: bool,
@@ -362,7 +362,7 @@ impl DsnDesign {
     }
 
     fn add_circle(
-        board: &mut Board<DsnRules>,
+        board: &mut Board<DsnMesadata>,
         place_pos: Point,
         place_rot: f64,
         pin_pos: Point,
@@ -390,7 +390,7 @@ impl DsnDesign {
     }
 
     fn add_rect(
-        board: &mut Board<DsnRules>,
+        board: &mut Board<DsnMesadata>,
         place_pos: Point,
         place_rot: f64,
         pin_pos: Point,
@@ -517,7 +517,7 @@ impl DsnDesign {
     }
 
     fn add_path(
-        board: &mut Board<DsnRules>,
+        board: &mut Board<DsnMesadata>,
         place_pos: Point,
         place_rot: f64,
         pin_pos: Point,
@@ -600,7 +600,7 @@ impl DsnDesign {
     }
 
     fn add_polygon(
-        board: &mut Board<DsnRules>,
+        board: &mut Board<DsnMesadata>,
         place_pos: Point,
         place_rot: f64,
         pin_pos: Point,
diff --git a/src/dsn/rules.rs b/src/dsn/mesadata.rs
similarity index 95%
rename from src/dsn/rules.rs
rename to src/dsn/mesadata.rs
index beba63d..267d3b7 100644
--- a/src/dsn/rules.rs
+++ b/src/dsn/mesadata.rs
@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 
 use crate::{
+    board::mesadata::MesadataTrait,
     drawing::rules::{Conditions, RulesTrait},
     dsn::structure::Pcb,
 };
@@ -21,7 +22,7 @@ impl DsnRule {
 }
 
 #[derive(Debug)]
-pub struct DsnRules {
+pub struct DsnMesadata {
     structure_rule: DsnRule,
     // net class name -> rule
     class_rules: HashMap<String, DsnRule>,
@@ -34,7 +35,7 @@ pub struct DsnRules {
     net_to_netclass: HashMap<usize, String>,
 }
 
-impl DsnRules {
+impl DsnMesadata {
     pub fn from_pcb(pcb: &Pcb) -> Self {
         let layer_ids = HashMap::from_iter(
             pcb.structure
@@ -87,7 +88,7 @@ impl DsnRules {
     }
 }
 
-impl RulesTrait for DsnRules {
+impl RulesTrait for DsnMesadata {
     fn clearance(&self, conditions1: &Conditions, conditions2: &Conditions) -> f64 {
         let (Some(net1), Some(net2)) = (conditions1.maybe_net, conditions2.maybe_net) else {
             return 0.0;
@@ -115,3 +116,7 @@ impl RulesTrait for DsnRules {
         largest
     }
 }
+
+impl MesadataTrait for DsnMesadata {
+    //
+}
diff --git a/src/dsn/mod.rs b/src/dsn/mod.rs
index eb845a6..f1de5cf 100644
--- a/src/dsn/mod.rs
+++ b/src/dsn/mod.rs
@@ -1,4 +1,4 @@
 mod de;
 pub mod design;
-pub mod rules;
+pub mod mesadata;
 mod structure;
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 4a7aac8..8073405 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -7,16 +7,13 @@ use topola::{
         invoker::{Invoker, InvokerError},
         Autorouter,
     },
-    board::Board,
-    drawing::{
-        graph::{GetLayer, GetMaybeNet},
-        rules::RulesTrait,
-    },
-    dsn::{design::DsnDesign, rules::DsnRules},
+    board::{mesadata::MesadataTrait, Board},
+    drawing::graph::{GetLayer, GetMaybeNet},
+    dsn::{design::DsnDesign, mesadata::DsnMesadata},
     graph::GetNodeIndex,
 };
 
-pub fn load_design_and_assert(filename: &str) -> Invoker<DsnRules> {
+pub fn load_design_and_assert(filename: &str) -> Invoker<DsnMesadata> {
     let design = DsnDesign::load_from_file(filename).unwrap();
     let mut invoker = Invoker::new(Autorouter::new(design.make_board()).unwrap());
 
@@ -32,7 +29,7 @@ pub fn load_design_and_assert(filename: &str) -> Invoker<DsnRules> {
     invoker
 }
 
-pub fn replay_and_assert(invoker: &mut Invoker<DsnRules>, filename: &str) {
+pub fn replay_and_assert(invoker: &mut Invoker<DsnMesadata>, filename: &str) {
     let file = File::open(filename).unwrap();
     invoker.replay(serde_json::from_reader(file).unwrap());
 
@@ -59,7 +56,7 @@ pub fn replay_and_assert(invoker: &mut Invoker<DsnRules>, filename: &str) {
 }
 
 pub fn assert_single_layer_groundless_autoroute(
-    autorouter: &mut Autorouter<impl RulesTrait>,
+    autorouter: &mut Autorouter<impl MesadataTrait>,
     layername: &str,
 ) {
     let unionfind = unionfind(autorouter);
@@ -125,7 +122,7 @@ pub fn assert_single_layer_groundless_autoroute(
 }
 
 /*pub fn assert_number_of_conncomps(
-    autorouter: &mut Autorouter<impl RulesTrait>,
+    autorouter: &mut Autorouter<impl MesadataTrait>,
     conncomp_count: usize,
 ) {
     let unionfind = unionfind(autorouter);
@@ -137,7 +134,7 @@ pub fn assert_single_layer_groundless_autoroute(
 }*/
 
 pub fn assert_band_length(
-    board: &Board<impl RulesTrait>,
+    board: &Board<impl MesadataTrait>,
     source: &str,
     target: &str,
     length: f64,
@@ -149,7 +146,7 @@ pub fn assert_band_length(
     assert!((band_length - length).abs() < epsilon);
 }
 
-fn unionfind(autorouter: &mut Autorouter<impl RulesTrait>) -> UnionFind<NodeIndex<usize>> {
+fn unionfind(autorouter: &mut Autorouter<impl MesadataTrait>) -> UnionFind<NodeIndex<usize>> {
     for ratline in autorouter.ratsnest().graph().edge_indices() {
         // Accessing endpoints may create new dots because apex construction is lazy, so we access
         // tem all before starting unionfind, as it requires a constant index bound.