Canonical structural properties

Property blobs are open MessagePack objects, but structural meaning is deliberately narrow. Writers and readers use one key per structural concept; arbitrary application properties are not silently promoted through aliases.

Context	Current structural field	Meaning
Property-graph edge	relationship	The edge name used by Cypher, UQL, GraphQL, RDF projection, reasoning, mining, jobs, and TMS
Typed EdgeData	relationship	The serialized typed-edge relationship
Knowledge currency node	node_type	KnowledgeRow.kind and modality dispatch
RDF node typing	type	The RDF rdf:type value folded onto the node for RDF/property-graph querying; this is node data, never an edge relationship
Cypher primary / secondary labels	node_type, labels	MATCH labels, node-map projection, CREATE/MERGE, label removal, and db.labels()

The removed edge keys type, rel_type, relation, and relationship_type are not accepted as relationship aliases. A payload may still contain an ordinary property named type; it does not make an edge typed. Untyped edges remain valid topology, but typed traversals do not fabricate a relationship for them, and GraphQL schema introspection rejects an edge that needs a relationship field but has none.

For Cypher, payload fields named type or label are also not node-label aliases. A bare RETURN n materializes the node property map with an authoritative virtual id (the graph key) and canonical node_type; callers do not need a client-side node-id-to-map projection step.

External connectors normalize source-native schema at ingress and persist relationship. They do not store source aliases alongside the canonical field. This keeps every query surface and reasoning subsystem on the same physical representation.

scripts/check_canonical_property_schema.py enforces this contract in pre-commit and Rust CI. The gate is intentionally scoped to structural readers and writers, so it does not ban legitimate domain payloads named type.