| name | nw-algebraic-design-protocol |
| description | The METHOD for finding a design — name observations and equality before constructors, then follow any contradiction to the type or observation that causes it. Use when a design decision is contested, a law has exceptions, a census or model keeps producing wrong answers, or a representation change must preserve meaning. Complements nw-fp-algebra-driven-design, which catalogues the structures; this says how to arrive at one and what to do when it breaks. |
Algebraic Design Protocol
nw-fp-algebra-driven-design catalogues structures; this finds a design and
traces a false law. Load both for a compositional core; load this alone for a
design that keeps giving wrong answers.
nWave sequencing choice. State observations/equality before an algebra;
this is project synthesis, not a universal ADD claim.
Cross-layer authority (ADR-SSOT-002 §6a). One language-agnostic procedure
for declared target-boundary layers: domain, application/ports, adapter/
integration, infrastructure/recovery. targets[].boundary/contract-shape
sets applicability without a persisted field. OO/FP catalogues are projections,
never competitors.
1. Observations and equality, before anything else
State what a user can meaningfully observe. Then define x ≈ y as agreement
under that observation set — never structural equality chosen because it was easy
to implement.
Inventory each observation, its result type, and what it cannot distinguish.
That last column is the one that pays: a Boolean result is usually too weak the
moment composition needs the remaining input or state.
If several observations repeat the same traversal, look for one more primitive
transition the others project from.
2. Constructors one at a time, each with an equation
After adding a constructor, write at least one equation relating it to an
observation or an existing constructor. The web of equations IS the design.
A law with ignored arguments, many exceptions, or domain-specific flags signals a
fused concept. Split it before choosing a representation.
3. Follow a contradiction to the carrier — do not special-case it
This is the step that catches real defects, and the reason to load this skill
when something is already broken.
When a law fails, the cause is usually not the law. It is that the carrier —
the type you are observing through — cannot express the property. Order-insensitive
composition observed through an order-sensitive list is the textbook case.
Two honest resolutions: replace the carrier, or retract the law. Never
conceal the conflict with a special case, because a special case makes the model
agree with the data while still being wrong about the domain.
Worked anchor (nWave, 2026-08-06). A census asked "is this MODULE live?"
when liveness was a property of the VERB the module dispatched. The three verbs
disagreed, so the answer came back for whichever one dominated the text.
Measuring per-module was the wrong carrier, and no amount of scanning more
surfaces would have fixed it — the fix was to change what the unit was. The
unit comes from the SEMANTICS, not from the file system.
4. Keep the representation out of the public algebra
Persistence, tree shape, cache and optimisation are not part of the design.
Build a deliberately obvious reference encoding first; enforce canonical
reductions through smart constructors.
Generate values through the public surface, and state reachability and size
bounds explicitly. Generated counterexamples are candidate findings until a human
reviews them: an impossible minimal case is evidence to audit the generator
before blaming the implementation.
For every intended public value, trace admitted input through a public
constructor/producer and consumer to a public observation. The construction
graph must be acyclic from an admitted input, or name an explicit bootstrap;
a cycle with no seed proves neither inhabitation nor reachability.
5. Optimise by denotation, and prove the claim observationally
Seek a homomorphic denotation the other observations derive from. State the old
and new observation sets and the equivalence claim before changing the
representation, and protect it with generated terms on both sides.
Passing generated checks is evidence, not proof. Say which.
Stop conditions
The design is ready when every public constructor participates in a law or an
observation, equality has a stated scope, and tempting-but-false laws are
recorded rather than deleted — a future reader who rediscovers one needs to
know it was already refuted.
Escalate rather than paper over an unresolved observation, an incompatible
carrier, or a nondeterministic boundary whose effect model has not been stated.
Scope boundary
Candidate algebra/preservation only: BROAD_INPUT_DOMAIN needs broad generated
domain plus independent observation/falsifier; finite exhaustive/no law is
NOT_APPLICABLE. It selects no topology, aggregate, deployment or runtime wiring.
Cross-cutting invariants
Load nw-cross-cutting-invariants alongside this. In particular
gate:design-principles-gdp-1-9 and data:consumer-known-before-produced: an
observation nobody consumes is not an observation, it is a field.
