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]