The single relationship concept. Every edge, regardless of kind, carries:

Attribute	Type	Required	Meaning
edge	EdgeKind	yes	discriminant, see below
from	EntityId	yes	source
to	EntityId	yes	primary target (best candidate if uncertain)
provenance	Provenance	yes	how we know
anchor	SourceAnchor	yes	where observed
candidates	EntityId[]	no	possible targets when dispatch is uncertain; non-empty iff resolution was ambiguous
sourceFile	string	no	disambiguates which declaration site produced the edge (C# partial classes, TS declaration merging)

Rules

• Outgoing only, stored once. All inverse views — callers of X, subtypes of Y, importers of M, and children (the inverse of parent) — are derived in memory, never serialized. Only parent is a stored fact.
• Closure: from and to must resolve to a known entity or a stub — a tested property of every model.
• No self-reference: from ≠ to.

Edge kinds

Kind	From → To	Extra attributes	Notes
import	Module → Module		First-class layer: the only relation reliable ≈100% across all languages, hence the granularity for cross-language comparison. Rust has two levels (mod, crate)
inheritance	Type → Type		N edges for multiple inheritance (Python); optional MRO order left to profile notes
interfaceImplementation	Type → Type (interface/trait/protocol)		declared (Java implements) or derived (Go, TS structural) depending on language. For Rust/Clojure the anchor is the reified impl block
invocation	Invocable → Invocable	candidates	uncertain dispatch → provenance: dynamic-candidate + candidates list
access	Invocable → Structural	isRead: bool, isWrite: bool	field/variable reads and writes; a compound assignment sets both
reference	Entity → Type		type usage that is none of the above (declarations, generics, casts)
annotationUse	Entity → Type (annotation)	arguments: NamedArgument[]	a written annotation on any entity, with its arguments. The dedicated kind carries the values and lets a consumer select annotation usages without guessing from the target’s kind — which a stub target cannot answer
throws	Invocable → Type (exception)		a written throw statement whose static exception type resolved; the anchor is the throw SITE. A declared propagation clause (Java throws E) is a plain reference, not this
embedding	Type → Type		Go struct { Base } — neither inheritance nor attribute (method promotion); dedicated relation
traitUsage	Type → Trait (PHP)		PHP use TraitX; — kept as a usage edge, never flattened into the class
fileInclude	CodeFile → CodeFile		PHP include/require — the only file-to-file dependency in the metamodel

The order above is the order the header dictionary’s enum declares.

Relations: edges connect entities; are licensed per language profile (a profile lists which edge kinds its extractor can emit); carry a SourceAnchor and a Provenance.

Folded edges

Analyses do not read base edges directly: the analyzer folds them to --level module or --level type first, aggregating every base edge between two folded nodes into one arrow that carries the count, the set of base kinds and the set of provenances. A folded arrow is an inference about a group, not a written fact; what it aggregates is stated in every rendering.