Step 1 of the GSS content-matcher build (docs/design/counted-content-automaton.md).
A multiply-referenced `<xs:group>` expands to one copy-on-write-shared `Particle`
(GroupParticleMemo), but `Group`/`Term` are value types with no exposed identity,
so a content-model compiler cannot tell two references apart and inlines the group
per reference (the 2^K build the GSS matcher will close).
Group now carries a `definitionID: Int?`, stamped from a per-compile counter on
GroupParticleMemo when an expansion is first compiled, so every reference sharing
the memo key reuses the same stamped term and distinct definitions differ. It is
metadata only: Group is not Equatable/Hashable, so it perturbs no determinism or
restriction comparison, and it is nil for an inline group.
FP-neutral by construction (no consumer yet). Full in-repo suite green; the XSTS
buckets are unchanged (valid-schemas-rejected 0, invalid-schemas-accepted 8,
valid-instances-rejected 0, invalid-instances-accepted 14); swiftformat/swiftlint
clean. Step 2 (a call/return content-model build keyed on this id, alongside the
inlining oracle) consumes it.
Mihaela Mihaljevic
e81e4b4df6