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rdbms-playground/docs/adr/0000-record-architecture-decisions.md
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claude@clouddev1 9f15f386d5 docs(adr): design the DSL→SQL teaching echo (ADR-0038) + dependencies
Realises ADR-0030 §10 (the DSL→SQL teaching bridge) as a /runda'd design
set, before implementation:

- ADR-0037 (new): execution-time mode side-channel — SubmissionMode
  {Simple, Advanced, AdvancedOneShot} threaded Action→worker, output-only;
  redeems ADR-0033 Amendment 3's deferred follow-up. Replay stays silent.
- ADR-0038 (new): the teaching echo + full catalogue (Buckets A/B/C),
  the copy-paste round-trip contract, the three-category framework, and
  the Value→SQL-literal renderer. DDL + show-data centric (overlapping
  DML is SQL-first, so already SQL). Build-order deps recorded.
- ADR-0035 Amendment 2: standard-first dialect stance + ALTER COLUMN
  SET/DROP NOT NULL, SET/DROP DEFAULT, ISO SET DATA TYPE gap-fill.
- ADR-0033 Amendment 4: reclassifies the `update … --all-rows`
  non-fall-back as a bug; it now falls back to the DSL Update and echoes
  (keyed on adjacent `--`; spaced arithmetic preserved).
- ADR-0039 (new): EXPLAIN over advanced SQL — decision recorded, build
  deferred; supersedes ADR-0030 §13 OOS-2.
- ADR-0000: out-of-scope discipline (deferred vs rejected). README index
  updated for all of the above.

Reconcile CLAUDE.md: simple-mode column ops are implemented, not pending
(requirements.md C2/B2 already [x]).
2026-05-27 20:44:38 +00:00

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Markdown

# ADR-0000: Record architecture decisions
## Status
Accepted
## Context
The RDBMS Playground project will accumulate design decisions as it
grows. We want those decisions to be traceable, reviewable, and easy
to challenge later when context has changed.
## Decision
Record significant architecture and product decisions as Architecture
Decision Records (ADRs) in `docs/adr/`, using the Michael Nygard
format (Status, Context, Decision, Consequences). Files are numbered
sequentially with a four-digit prefix and a kebab-case slug, e.g.
`0001-language-and-tui-framework.md`.
Each ADR captures one decision. Superseding a decision means adding a
new ADR that references the old one and marking the old one as
"Superseded by ADR-NNNN".
ADRs document decisions, not speculation. An idea under discussion
belongs in conversation, an issue, or a design note — not an ADR. An
ADR is written once a decision has actually been made.
## Index discipline
`docs/adr/README.md` contains the canonical index of all ADRs.
Whenever an ADR is added, renamed, or has its status changed (e.g.
"Superseded by ADR-NNNN"), the index MUST be updated in the same
change. An ADR change without a corresponding index update is
incomplete.
The index lists ADRs in numerical order. Each entry shows the
number, title, and — where relevant — status annotations such as
"Superseded by ADR-NNNN" or "Deprecated".
## Out-of-scope discipline
ADRs (and the plans they spawn) lean heavily on "out of scope" language.
The phrase carries two very different meanings, and conflating them
misleads a later reader:
- **Deferred** — out of scope *for this plan / phase / step*, but a
reasonable thing to do later. A sequencing decision, effectively a
tracked TODO. Where possible, point at where it will be picked up.
- **Rejected** — considered and deliberately *not* done, on principle.
Durable. State the reason.
When writing an out-of-scope item, **say which kind it is** — e.g.
`OOS (deferred)` / `OOS (rejected: <reason>)`, or the equivalent in prose
— so a future reader can tell a standing decision from a not-yet. A bare
"out of scope" is ambiguous and tends to read, wrongly, as permanent.
(Motivating example: ADR-0030 §13 OOS-2 was a deferred scope exclusion
that read as a permanent rejection until ADR-0039 lifted it.)
## Consequences
- New significant decisions require an ADR before or alongside the
implementation that depends on them.
- Old decisions remain visible even after they are superseded.
- Reviewers can audit the rationale chain by reading `docs/adr/` in
order.
- The index in `README.md` stays trustworthy because keeping it
current is part of every ADR change, not an afterthought.