Rules runtime

Modeller.Rules is the reference implementation of the reusable rules-runtime contract. It exposes one deep two-stage interface:

RuntimeBindingResult RulesRuntime.Bind(
    FederationSnapshot snapshot,
    IEnumerable<LoadedContextPackage> packages,
    FunctionCatalogue functions,
    RuntimeLimits limits,
    CancellationToken cancellationToken = default);

EvaluationResult RuntimePlan.Evaluate(
    EvaluationRequest request,
    CancellationToken cancellationToken = default);

Binding reruns core semantic validation, checks exact snapshot locks and expression limits, and returns either an immutable runtime plan or ordered diagnostics. A plan retains no request state and is safe for concurrent reuse.

Requests and typed facts

An evaluation request identifies one Rule, supplies immutable values keyed by stable Fact IDs, supplies immutable evidence, and selects a trace level and disclosure policy. Language 1.0 supports Truth Fact values for its And expression slice. Unknown Fact IDs and mismatched value types produce an invalid result; values are never coerced.

The same operation evaluates decision tables. The initial Unique policy requires every complete Truth-Fact combination to match exactly one row. Binding rejects duplicate inputs, unresolved conclusions, overlapping rows, incomplete tables, and tables exceeding 16 inputs.

The Child Care 1.1 fixture classifies ACCS eligibility. Active enrolment plus supporting evidence selects Eligible; an inactive enrolment selects Ineligible without requiring irrelevant evidence through a wildcard cell; missing evidence remains indeterminate when it can change the classification.

Evaluation results

The interface represents the four statuses as distinct immutable types:

Cancellation throws normal cancellation control flow and publishes no partial evaluation result. Implementation defects are not converted into domain failures.

false AND missing is determined false because the missing Fact cannot change the conclusion. true AND missing is indeterminate. Missing information is never converted to false or null.

Findings, evidence, and explanations

Fact-expression finding codes are authored canonical meaning. The Child Care rule records accs.active-enrolment-confirmed, accs.supporting-evidence-confirmed, and accs.supporting-evidence-required; the runtime does not infer these from names. Findings carry deterministic local identities, dispositions, semantic references, and evidence references.

Evidence is preserved only when it supports a referenced Fact and the request's disclosure policy permits it. Public ACCS results omit protected supporting document metadata without changing the conclusion. Audience prose and next actions are deterministic projections from this structured result, as proved by the reviewed ACCS conformance fixtures.

Canonical traces and telemetry

None, Summary, and Full select canonical semantic detail without changing conclusions or findings. Full ACCS traces contain stable paths for the Rule and both Fact-expression steps. They exclude request IDs, timestamps, durations, host information, and sensitive Fact values.

OpenTelemetry is a later operational projection that may correlate spans to canonical paths and semantic IDs. OTEL availability, timing, sampling, and export failure never enter or delay the canonical result.

Determinism, limits, and concurrency

Runtime reference/1.0 orders definitions, diagnostics, findings, evidence, and traces semantically. The same immutable plan can evaluate requests concurrently without sharing facts, findings, evidence, traces, or cancellation.

RuntimeLimits bounds semantic steps, expression depth, request collection size, and canonical trace nodes. Work and trace exhaustion produce stable failed results at the same semantic step. Oversized request collections are invalid. Machine-dependent time and memory limits remain host controls rather than semantic results.

Declared functions and compatibility

FunctionCatalogue is explicitly versioned. Each IDeclaredFunctionAdapter has a stable ID and version, receives only typed arguments and the caller cancellation token, and returns a typed value or safe structured failure. Canonical language 1.0 declares no function-call expression, so the initial Child Care plan binds the empty none/1.0 catalogue.

The compatibility matrix records runtime contract reference/1.0. The reviewed Eligible and Information required fixtures are executable through the public bind-and-evaluate seam, as is the Unique Child Care decision-table fixture.