Effective Query Model Estimation Using Parsimonious Translation Model in Language Modeling Approach

摘要

The KL divergence framework, the extended language modeling approach has a critical problem with estimation of query model, which is the probabilistic model that encodes user's information need. At initial retrieval, estimation of query model by translation model had been proposed that involves term co-occurrence statistics. However, the translation model has a difficulty to applying, because term co-occurrence statistics must be constructed in offline. Especially in large collection, constructing such large matrix of term cooccurrences statistics prohibitively increases time and space complexity. More seriously, because translation model comprises noisy non-topical terms in documents, reliable retrieval performance cannot be guaranteed. This paper proposes an effective method to construct co-occurrence statistics and eliminate noisy terms by employing parsimonious translation model. Parsimonious translation model is a compact version of translation model and enables to drastically reduce number of terms that includes non-zero probabilities by eliminating non-topical terms in documents. From experimentations, we show that query model estimated from parsimonious translation model significantly outperforms not only baseline language modeling but also non-parsimonious model.