AONT100–199 — Link Composition

The AONT100–199 range covers runtime structural validation of link descriptors and per-domain registration invariants that surface during OntologyGraphBuilder.Build(). The diagnostics in this slice — currently AONT040 and AONT041 — fire before any cross-domain resolver runs, so the message names the original multi-registration or duplicate registration rather than a downstream “unresolvable” error. They throw OntologyCompositionException, whose Diagnostics property carries an ImmutableArray<OntologyDiagnostic> of every diagnostic that fired during the failed build.

Diagnostic table

Code	Severity	Title	Message	Fix	Since
AONT040	Error (runtime)	Duplicate ObjectType name within domain	Object type name <name> is registered twice in domain <domain>. First registration: CLR type <typeA>. Second registration: CLR type <typeB>. Either remove one registration, or specify distinct names via Object<T>("name", ...)	Remove one of the duplicate registrations, or give one of them a distinct name via Object<T>("alternate-name", ...). The runtime check throws OntologyCompositionException before any cryptic dictionary error from downstream code.	2.4.1
AONT041	Error (runtime)	Multi-registered descriptor identity in link	descriptor identity <clrType-or-symbolKey> has multiple registrations (<domain>.<name>, …) but is also referenced as a link target / declares outgoing links / is declared as the source of a cross-domain link. Multi-registered types cannot participate in structural links. See #32 for a future relaxation path. Several sub-forms exist: CLR-simple-name fallback (HasMany<TLinked> against a multi-registered CLR type), descriptor-identity-by-registration, and an explicit-name divergence form (a link target registered with an explicit non-default name).	Drop the duplicate registration so the type has a single descriptor identity, or remove the link. Leaf types may remain multi-registered as long as they participate in no links anywhere. The explicit-name divergence form is fixed by registering the link target under the default name.	2.4.1

AONT041 is currently strict (leaf-only multi-registration)

The diagnostic rejects every link that touches a multi-registered descriptor identity — as target, as source, or via cross-domain wiring. Issue #32 tracks a relaxation candidate; there is no concrete consumer for relaxed semantics yet, so the strict rule stands. Plan for single-registration when a type participates in structural links.

Codes referenced in source comments but not yet emitted

The codes below appear in source-code comments as forward-looking placeholders. No DiagnosticDescriptor or OntologyDiagnostic literal currently emits them — they are reserved for future link-composition diagnostics.

Code	Status
AONT042	Reserved. Referenced in OntologyGraphBuilder.cs as part of the link-composition diagnostic family (“AONT040/AONT042-style messaging”). No descriptor yet.