Reverse relationships are derived

Context

A document names the documents it rests on, amends or replaces, and a spec page names the documents it reflects. Every one of those relationships has a reverse: what rests on this document, what amends it, what replaced it, which pages reflect it. A reader wants both directions. Under ADR-0001 a terminal document is never modified, so the reverse of a relationship formed after a document froze cannot be written into it.

Decision

Front matter records forward relationships only: depends, updates and obsoletes on an RFC or ADR, and includes on a spec page. Every reverse relationship is derived by the tooling from the forward ones across the whole repository and published in the generated index. Nothing derived is ever written into a document. The same derivation yields three facts about a document: it is effectively obsolete when an accepted document obsoletes it, it is implemented when it is accepted and some spec page includes it, and a spec page is stale when it includes something effectively obsolete.

Alternatives

No alternatives were weighed.

Consequences

Easier:

• Recording a new relationship touches one document, the one making the claim.
• A frozen document acquires reverse relationships for as long as the repository lives, with no edit to it.

Harder:

• A document read on its own shows only what it knew when written. What later referred to it is elsewhere.

Constrained:

• The tooling will have to read every document to answer a question about any one of them.
• The derived relationships will need somewhere to be published, since they live in no document.
• Whether a document is obsolete, implemented or stale will be computed from the graph, not stated in front matter.

Sources

• PROCESS.md at 9654fe2, section Front matter, states that only forward relationships are recorded and gives the reason: a frozen document cannot be edited to record what happened to it later. This sets created and decided.
• docs/ARCHDOC.md at 9654fe2a, section Relationships and derivation, lists what is derived and defines effectively obsolete, implemented and stale.
• The decision was taken in a design session before that commit, not publicly available, and first written down on 2026-09-13. The date it was taken is not recalled.