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First provide a summary of the paper, and then address the following criteria: Quality, clarity, originality and significance. The authors propose to formalize the notion that the ranking function depends only on the object features, and not the order in which the documents are presented. This is a good idea, but the proposed notion of exchangeability is too strict in my opinion: we can capture the intended notion without the strict equality in eqn 1 and 2. We just want the order of the scores to be preserved, not their exact values. In terms of clarity, there are sections that are quite unclear, as pointed out below. You should define symmetric function in the proof of Thm 3.2.