Formal Coverage Metrics: Beyond Green Proof Counts: Inputs and Outputs

Inputs and outputs contract

Inputs and Outputs for Formal Coverage Metrics: Beyond Green Proof Counts is anchored on non-vacuous closure rate, counterexample turnaround, and residual-risk trend by requirement class. Convert outcomes into assumption-aware, evidence-backed actions.

INPUTS
  - requirement intent and risk tier
  - property scope and temporal contract
  - assumption model and reset policy
  - tool/engine metadata and reproducibility tags

OUTPUTS
  - evidence-backed root-cause classification
  - owner-signed mitigation proposal
  - validation matrix and rollback triggers
  - signoff recommendation

Ownership split

OWNERSHIP LAYERS - Formal Coverage Metrics: Beyond Green Proof Counts

+----------------------+--------------------------------+--------------------------------+
| Team                 | Primary responsibility         | Closure artifact               |
+----------------------+--------------------------------+--------------------------------+
| formal verification owner | property and model integrity      | assumptions and proof packet   |
| rtl owner | implementation root-cause closure | RTL fix and replay evidence    |
| Formal Coverage & Signoff owner | signoff governance and rollout    | risk memo + acceptance gates   |
+----------------------+--------------------------------+--------------------------------+

Formal deep dive

Signoff quality is requirement-centric and must integrate proof status, reachability, bounded limits, and waiver governance.

Concept diagram

FORMAL SIGNOFF PYRAMID

requirements -> properties and covers -> quality metrics -> waiver governance -> release decision

Metric graph

SIGNOFF CONFIDENCE TREND

fully proven critical    ███████
bounded-only critical    ████
unexplained cover gaps   ███

Metrics and artifacts to collect

• requirement-to-proof closure map

• critical cover reachability and gap aging

• bounded-only risk register

• waiver debt with owner and expiry

Mini case study

A release review blocked signoff until bounded-only properties were paired with explicit residual-risk and replay plans.

Debug branches

• Separate status color from proof quality dimensions.

• Treat unreachable critical covers as signoff blockers.

• Document bounded-horizon rationale with architecture limits.

Senior review question

Ask: which requirement intent is proven, under which assumptions, and what residual risk remains?

Key takeaways

• Tie each proof claim to assumption boundaries and reachability evidence.

• Prefer minimal reversible fixes and preserve legal behavior visibility.

Common pitfalls

• Treating runtime reduction as proof-quality improvement without audits.

• Declaring closure while critical covers remain unreachable.

• Using broad waivers instead of first-divergence root-cause ownership.

Handoff explanation

Inputs should include assumptions, reset semantics, and property intent classes.

Outputs should include counterexample classification, closure confidence, and residual-risk labeling.