Document — the in-memory tree resulting from parsing a projectfile.{toml,yaml,json} file under this specification, regardless of the on-disk encoding.
Encoding — one of TOML, YAML, or JSON. The file extension identifies the encoding (Section 3.1).
Producer — any agent that writes or modifies a document.
Consumer — any agent that reads a document.
Validator — a consumer that verifies a document against the JSON Schema derived from this specification.
Coordinates — the (identity.namespace, identity.name) pair that uniquely identifies a project within the ecosystem (Maven-style).
Reserved key — a top-level key defined by this specification. Lowercase, single segment, no dots. $schema and spec_version are reserved by exception (see §3.4).
Extension namespace — a nested-mapping path from the document root whose first segment is not a reserved key. The full path forms a reverse-DNS namespace (e.g., com.example.build). Each segment matches ^[a-z0-9][a-z0-9-]*$ and the path contains at least 2 segments.