ADR 0002 — Typed runtime model, not a generalised knowledge graph

Status: Accepted

Context

The corpus has relationships, which invites a generic graph abstraction. §28 forbids creating one merely because relationships exist.

Decision

Model concrete domain types (F). Relations are a closed set of observed cases plus an explicit Other. No triple store, no schemaless node/edge soup.

Evidence

OBSERVED: only 6 canonical relation kinds exist in the entire corpus (related_documents, source_rep, supersedes, superseded_by, originates, prerequisite). A general graph engine would be built to carry six edge types.

Alternatives

RDF/property graph — rejected: unjustified by data volume or variety.

Consequences

Adding a relation kind is a code change. Given six kinds have appeared over the corpus's life, that is an acceptable cadence.

Reversibility

Moderate — the typed edges could be projected into a general graph later.