Parent: stages-and-gates
| Domain | Stage (free) | Gate (verifiable checkpoint) |
|---|---|---|
| Compiler | lex / parse / typecheck / optimize / codegen | well-formedness — the type checker rejects ill-typed code ("well-typed programs don't go wrong" = the gate) |
| CI/CD | build / test / deploy | quality gate: tests green, coverage, lint, signature |
| TDD | write test / write code / refactor | red → green → ratchet (no green turns red) |
| Clinical trials | Phase I/II/III study design | safety → efficacy gates; kill bad drugs early; escalating cost |
| VC funding | seed/A/B company growth | milestone check before the next round (staged financing = compound option) |
| Aerospace reviews | engineering between reviews | PDR → CDR → TRR → FRR; TRL 1–9 readiness |
| Cell cycle | G1 / S / G2 / M biochemistry | literal checkpoints: G1/S (DNA intact), G2/M (replication done), spindle SAC (chromosomes attached) |
| Stage-Gate (Cooper) | Scoping / Business-Case / Development | Go / Kill / Hold / Recycle (deliverables + criteria) |
| Three-act drama | each act's writing | plot points (turning points) push act → act |
| Due process | investigation / trial / sentencing | grand jury (enough to indict); "beyond reasonable doubt" |
| Courses | how you study a course | prerequisites / exams unlock the next |
Recurring motif: many gate criteria are type / well-formedness checks — the gate type-checks the stage's output.