  Transformer-based models are nowadays state-of-the-art in ad-hoc Information
Retrieval, but their behavior is far from being understood. Recent work has
claimed that BERT does not satisfy the classical IR axioms. However, we propose
to dissect the matching process of ColBERT, through the analysis of term
importance and exact/soft matching patterns. Even if the traditional axioms are
not formally verified, our analysis reveals that ColBERT: (i) is able to
capture a notion of term importance; (ii) relies on exact matches for important
terms.
