Add unknown ranges and open object values

README.md

@@ -9,7 +9,8 @@ It is designed around a lightweight Rust library:
 - no filesystem access in the library core
 - concrete and abstract values with constraints and defaults
 - asymmetric range refinement with `narrower as wider`
-- homogeneous associative-array schemas with `{...valueSchema}`
+- homogeneous associative-array schemas with `{...valueSchema}` and object rest constraints
+- the safe top range `Unknown`, which remains abstract until refined, defaulted, or supplied concretely
 - deterministic expression evaluation
 - optional regex support behind a Cargo feature
 - browser playground support through WebAssembly
@@ -26,6 +27,7 @@ decodal = "0.3.0"
 ## Derive support
 
 For embedded Rust applications, Decodal can generate a schema and typed decoder from a Rust struct with the `derive` feature.
+Map fields marked with `#[decodal(rest)]` receive additional object fields; `BTreeMap<String, Data>` corresponds to `...Unknown`.
 
 ```toml
 [dependencies]
@@ -47,7 +49,7 @@ struct Service {
 
 The derive implements:
 
-- `DecodalSchema`, which produces a host schema for `Engine::bind_global`
+- `DecodalSchema`, which produces a `Value` range for `Engine::bind_global`
 - `DecodalDecode`, which converts materialized `Data` into the Rust struct
 
 ## CLI