Implementation Selection Guide

Select the smallest profile that accurately represents the relying decision. Do not claim a higher profile merely because the implementation can parse its records.

Decision path

1. Discovery only: implement Profile A and ARPA-Core.
2. Operational accountability without delegated transactions: add Relations, Assurance and Evidence for Profile B.
3. Action-specific delegated authority: add Authority and enforcement integration for Profile C.
4. Rights-affecting, fiduciary, safety-critical or cross-governance action: implement Profile D and document independent governance, recognition, revocation convergence and redress evidence.

Required deployment declaration

Every implementation publishes a Conformance Declaration identifying supported modules, profile, identifier schemes, proof suites, transports, freshness targets, revocation targets and known limitations.

Fail behaviour

Discovery MAY return stale projections with warnings where policy permits. Authority evaluation MUST return indeterminate or deny when current status, authority, required assurance or proof validity cannot be established. Missing evidence MUST NOT become an affirmative result.

Runtime implementation selection

The Python reference service demonstrates the stateful registry and API architecture. The repository also carries an independent TypeScript implementation track whose first purpose is cross-runtime conformance assurance. Implementers SHOULD choose a runtime according to deployment needs, but conformance claims are determined by supported ARPA modules and profiles rather than implementation language.