M4D-MKLab/ITI-CERTH Participation in TREC Deep Learning Track 2021

Our team’s (CERTH ITI M4D) goal in the TREC Deep Learning Track was to study how the Con-
textualized Embedding Query Expansion (CEQE) [1] method performs in such setting and how our
proposed modifications affect the performance. In particular, we examine how CEQE performs with
the addition of bigrams as potential expansion terms, and how an IDF weight component affects
the performance. The first run we submitted is produced by a query expansion pipeline that uses
BM25 for retrieval and CEQE with the IDF modification for query expansion. The second submitted
run used a modification of CEQE with the addition of bigrams as candidate expansion terms and a
re-ranking step using CEDR. Our runs showed promising results, especially for Average Precision.