compare-pair

Purpose

Execute one pairwise comparison under a declared criterion and return a winner, confidence, tie status, and reasons.

Input contract

required: [item_a, item_b, comparison_criterion, comparison_model, evidence_register]
optional: [tie_rule, prior_ratings]
constraints: [criterion direction and evidence scope are fixed before comparison]

Procedure

1. Verify that both items are comparable under the same criterion and evidence scope.
2. Assess item A and item B symmetrically, recording criterion-level evidence and limitations.
3. Select A, B, or tie; assign confidence on the declared scale and explain the decisive contrast.
4. Return the comparison record without updating global ratings.

Output contract

produces: [pairwise_result, confidence, rationale, evidence_gaps]
delta_fields: [findings, evidence_updates, uncertainties, decisions]

Quality gates

• The result includes exactly one winner or an explicit tie, confidence, criterion, and symmetric evidence notes.
• Confidence cannot exceed the support of the weaker side of the comparison.

Failure and counterexamples

Do not compare items with different scopes or criteria. If evidence is asymmetric or incomparable, return unresolved rather than forcing a winner.

Provenance map

• resolved: comparison-executor
• resolved: gap-pairwise-judgment