Pattern Proposal: Application Service and Domain Engine Separation

Summary

Separate application-level transaction coordination from pure domain calculation engines.

Candidate Pattern

• ID: service-engine-separation
• Classification: architectural
• Maturity: strategic_direction
• Type: emerging

Observed Signals

No specific signals listed.

Evidence

Supporting Evidence

• src/cas_runner/governance/governance_action_service.py (GovernanceActionService) - Orchestrates governance use cases across engines.
• src/cas_runner/governance/governance_action_engine.py (GovernanceActionEngine) - Performs concrete action execution and state transition validation.
• src/cas_runner/governance/compliance_engine.py (ComplianceEngine) - Evaluates compliance rules independently of the action service.

Scope Assessment

• Evidence Strength: high
• Confidence: high
• Applies to: ideas-to-life-cas

Rationale

• Intent: Keep domain policy logic isolated from environment-specific I/O, error handling, and orchestration mechanisms.
• Context: Governance evaluation requires both pure rule evaluation (compliance checks) and orchestration with the local file system or external triggers.
• Force: Domain engines should not be tightly coupled to CLI or API parameter conventions.
• Force: Application services must be able to orchestrate multiple engines within a single workflow.

Traceability

Artifact source: proposed-patterns