docs: add ADR template and contribution process

CONTRIBUTING.md

@@ -7,36 +7,36 @@ Thank you for your interest in contributing to the Global Type System (GTS) Spec
 ### Prerequisites
 
 - **Git** for version control
-- **JSON Schema validator** (optional, for testing schema examples)
-- **Python 3.8+** (optional, for running reference implementations)
+- **Node.js 20+ and `ajv-cli`** (optional, for validating JSON Schema examples as CI does)
+- **Python 3.9–3.14** (optional, for working on the conformance test suite)
+- **Docker** (optional, and recommended for running the conformance test suite)
 - **Your favorite editor** (VS Code with JSON Schema support recommended)
 
 ### Development Setup
 
 ```bash
 # Clone the repository
-git clone <repository-url>
+git clone https://github.com/GlobalTypeSystem/gts-spec.git
 cd gts-spec
 
-# Optional: Install Python dependencies for reference implementations
-pip install jsonschema
-
-# Optional: Install JSON Schema validator
+# Optional: install the JSON Schema validator used by CI
 npm install -g ajv-cli
 ```
 
+The conformance tests run against an external GTS implementation over HTTP; this repository does not contain a reference implementation. See [`tests/README.md`](tests/README.md) for Docker and local Python setup.
+
 ### Repository Layout
 
 ```
 gts-spec/
-├── README.md                 # Main specification document
+├── README.md                 # Normative specification
 ├── CONTRIBUTING.md           # This file
-├── LICENSE                   # License information
-└── examples/                 # Example GTS Types and instances
-    ├── events/               # Event-related examples
-    │   ├── types/            # GTS Type Schemas (JSON Schema documents)
-    │   └── instances/        # JSON instance examples
-    └── ...                   # Other domain examples
+├── LICENSE                   # License
+├── NOTICE                    # Attribution notices
+├── adr/                      # Architecture Decision Records (+ template.md)
+├── examples/                 # GTS Types and Instances in JSON, YAML, and TypeSpec
+├── tests/                    # Implementation-independent HTTP conformance tests
+└── .github/workflows/        # CI and release workflows
 ```
 
 ## Development Workflow
@@ -57,16 +57,26 @@ Use descriptive branch names:
 
 Follow the specification standards and patterns described below.
 
+#### Specification changes require an ADR
+
+Any proposal that adds normative behavior to the specification or intentionally changes existing normative behavior **MUST go through the Architecture Decision Record (ADR) process**. Start by copying the project-adapted MADR [`ADR template`](adr/template.md) to the next sequentially numbered file under [`adr/`](adr/) and fill in all applicable sections. The specification, tests, and examples must reference or implement the decision where applicable.
+
+Open the pull request with the ADR already at **`Status: Accepted`** — the decision is what is under review, so accepting the ADR *is* merging the pull request. There is no separate approval step and no `Proposed` state in the repository: an ADR on `main` is accepted by definition. A decision that is later replaced keeps its file and moves to `Status: Superseded`, with `Superseded by` pointing at the ADR that replaces it (and that ADR's `Supersedes` pointing back). The ADR may be reviewed in its own pull request or together with the resulting specification change; either way it must not be merged before the reviewers agree on the decision itself.
+
+A confirmed bug fix does not require a new ADR when it only restores behavior already established by the specification or an accepted ADR. If fixing the issue requires choosing new semantics, it is a specification change and therefore requires an ADR.
+
 ### 3. Validate Your Changes
 
 ```bash
-# Validate all schemas in a directory
-ajv compile --strict=false -s "examples/events/types/*.schema.json"
+# Validate the JSON Schema examples covered by CI
+ajv compile -s "examples/*/types/*.schema.json" --strict=false
 
-# Run Python reference implementation tests (if available)
-python -m pytest tests/
+# Run the conformance tests against a GTS server already listening on port 8000
+python -m pytest tests/ --gts-base-url http://127.0.0.1:8000
 ```
 
+Run the checks relevant to the files you changed. JSONC, YAML, TypeSpec, nested example directories, and unresolved `gts://` references may require their own format-aware validation in addition to the CI command above. For test-suite setup and targeted test invocations, follow [`tests/README.md`](tests/README.md).
+
 ### 4. Commit Changes
 
 Follow a structured commit message format:
@@ -113,8 +123,9 @@ Specification development guidelines:
 
 - Follow GTS identifier format rules strictly
 - Ensure all schemas use correct `$id` values
-- Validate schemas against JSON Schema Draft 7 or later
+- Declare the intended JSON Schema dialect with `$schema` and use keywords valid for that dialect; GTS is dialect-agnostic, while repository examples generally use Draft-07 for interoperability
 - Include both GTS Type Schemas (the canonical JSON definitions of types) and GTS Instance examples
+- Keep normative specification changes, conformance tests, and examples aligned
 - Document any deviations or implementation-specific choices
 
 ## Releases
@@ -139,8 +150,8 @@ When the specification moves to the next minor version (e.g. `0.11` → `0.12`),
 Releases are produced from `github.com/GlobalTypeSystem/gts-spec`. The workflow is restricted to that repository; pushing a tag from a fork has no effect.
 
 ```bash
-git tag v0.11.3
-git push origin v0.11.3
+git tag vX.Y.Z
+git push origin vX.Y.Z
 ```
 
 The [`Release Tests Image`](.github/workflows/release-tests-image.yml) workflow:

README.md

@@ -1622,6 +1622,7 @@ Given an inheritance chain `S₀ → S₁ → … → Sₙ`:
   - **`null` at any depth deletes that key** from the effective object (per RFC 7396). The principal use case is to revert an ancestor-set value and let the trait-schema's `default` re-apply via the materialization step described in the Completeness check below — that is, a descendant writes `"<key>": null` to "fall back to the schema default" without picking a specific value. If the deleted key is `required` and has no `default`, the completeness check (OP#13) fails for non-abstract types (the descendant must then either mark itself abstract or accept that "delete + required + no default" is an unresolvable contract). Authors who want `null` as an *intended* trait value cannot express it via this merge and must use a sentinel value documented as part of the trait shape.
   - Defaults declared in the effective trait-schema MUST be materialized into the effective traits object before the Completeness check runs (per ADR-0003): for every property declared in the effective trait-schema with a `default` and not present in the chain-merged object, the registry MUST substitute the default value. The Completeness check below (OP#13) operates on the resulting *materialized* effective traits object.
   - A publisher who wants a trait value to be **locked** across all descendants of a base type SHOULD declare `"const": <value>` for that property in `x-gts-traits-schema`. A descendant attempting to override the value will fail the standard JSON Schema validation that runs against the effective trait-schema (per the Completeness check below). No GTS-specific "immutability" rule is required — `const` is the mechanism.
+  - `const` constrains the **value** of a property, not its presence: per standard JSON Schema it asserts nothing when the property is absent. A publisher who additionally wants the trait to survive an RFC 7396 `null` deletion SHOULD either list the property in the containing object schema's `required` array (deletion then fails the Completeness check for non-abstract types) or declare a `default` equal to the `const` value (deletion then becomes a no-op, since materialization restores the value before validation). This is the general presence rule for traits — it is not specific to `const`: any optional inherited trait without a `default` can be removed by a descendant.
   - A descendant MAY redeclare a trait value with the same value the ancestor already declared (idempotent restatement).
   - See [`adr/0004-x-gts-traits-merge-strategy.md`](adr/0004-x-gts-traits-merge-strategy.md) for the rationale.
 

adr/0001-derivation-form.md

@@ -56,6 +56,9 @@ This ADR does **not** make GTS a [JSON Schema Dialect](https://json-schema.org/l
 
 ## Considered Options
 
+- Option 1 — Strict canonical form
+- Option 2 — GTS Type Schema as a JSON Schema Extension (dialect-agnostic) *(chosen)*
+
 Both options use the same running example.
 
 ### Running example used in this section
@@ -207,7 +210,7 @@ P-OK validates; P-BAD fails. Syntactically valid and semantically compatible —
 
 ## Decision Outcome
 
-Chosen: **Option 2 — GTS Type Schema as a JSON Schema Extension (dialect-agnostic).**
+Chosen option: **Option 2 — GTS Type Schema as a JSON Schema Extension (dialect-agnostic).**
 
 Key normative consequences:
 

adr/0002-x-gts-traits-schema.md

@@ -41,7 +41,12 @@ ADR-0001 commits GTS to being an **extension of JSON Schema** (dialect-agnostic;
 
 ## Considered Options
 
-Two options. Option 2 has two sub-variants (2A and 2B) which we evaluate inside Option 2.
+- Option 1 — Trait-type as a separately-registered GTS Type (URI value)
+- Option 2 — `x-gts-traits-schema` is a JSON Schema subschema, in two sub-variants:
+  - Option 2A — Subschema + implicit chain aggregation *(chosen)*
+  - Option 2B — Subschema + explicit composition by the author
+
+Option 2's sub-variants share the keyword's value space and differ only in who composes the declarations along the chain; they are evaluated inside Option 2 below.
 
 ### Option 1 — Trait-type as a separately-registered GTS Type (URI value)
 
@@ -229,7 +234,7 @@ By construction, any value satisfying the effective trait-schema also satisfies
 
 ## Decision Outcome
 
-Chosen: **Option 2A — `x-gts-traits-schema` is a JSON Schema subschema (object OR boolean); the registry composes declarations along the `$id` chain via `allOf`.**
+Chosen option: **Option 2A — `x-gts-traits-schema` is a JSON Schema subschema (object OR boolean); the registry composes declarations along the `$id` chain via `allOf`.**
 
 Normative consequences:
 

adr/0003-x-gts-traits-completeness.md

@@ -92,6 +92,10 @@ ADR-0001 commits GTS to being an extension of JSON Schema (dialect-agnostic); AD
 
 ## Considered Options
 
+- Option 1 — No spec-level enforcement (author's responsibility)
+- Option 2 — Validate at instance creation time
+- Option 3 — Validate at type registration (fail fast) *(chosen)*
+
 Three top-level options on **when (or whether) to enforce completeness**.
 
 ### Option 1 — No spec-level enforcement (author's responsibility)
@@ -223,7 +227,7 @@ Three ways to make the registration succeed:
 
 ## Decision Outcome
 
-Chosen: **Option 3 — validate at type registration; non-abstract types MUST be complete.**
+Chosen option: **Option 3 — validate at type registration; non-abstract types MUST be complete.**
 
 ### Definition of "complete"
 
@@ -254,7 +258,7 @@ At the registration of type T:
 - **Non-abstract type with required-no-default and no explicit value.** Registration fails. Author resolves by (a) providing `x-gts-traits` value, (b) declaring a `default` in the schema, or (c) marking the type abstract.
 - **Final non-abstract type.** Same rule as any non-abstract — must be complete. No special bullet needed.
 
-## Implications
+### Implications
 
 - **OP#13 (Schema Traits Validation)** includes this rule; the operation explicitly conditions the completeness step on `x-gts-abstract != true`.
 - **§9.7.5** carries the normative wording of the completeness check in the "Validation" bullet block, expressed in terms of "non-abstract types."