21. Validation is a rule engine, and conformance is a profile of it

Date: 2026-09-13

Status

Accepted. Amended by 36 on 2026-09-26: the engine and the structural profile live in the core, the PDF/A and PDF/UA profiles in the AdCodicem.Pdf.Conformance satellite, and rule identifiers follow the grammar that record gives.

Context

Repair, conformance and every later guarantee are expressed in terms of findings. Two validators with two vocabularies would mean two answers to "is this document sound?".

Decision

Validation lands immediately after reading (M02), as the structural profile of a rule engine whose findings carry stable identifiers. PDF/A and PDF/UA arrive later (M20) as further profiles, not as a separate validator.

Consequences

• Consequence — rule identifiers are public API from the day they ship, and docs/website/docs/reference/validation-rules.md documents them.

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Recorded as D20 before this project adopted Architecture Decision Records; the identifier still appears in commit messages and in CLAUDE.md.