Passage retrieval based on language models

Previous research has shown that passage-level evidence can bring added benefits to document retrieval when documents are long or span different subject areas. Recent developments in language modeling approach to IR provided a new effective alternative to traditional retrieval models. These two streams of research motivate us to examine the use of passages in a language model framework. This paper reports on experiments using passages in a simple language model and a relevance model, and compares the results with document-based retrieval. Results from the INQUERY search engine, which is not based on a language modeling approach, are also given for comparison. Test data include two heterogeneous and one homogeneous document collections. Our experiments show that passage retrieval is feasible in the language modeling context, and more importantly, it can provide more reliable performance than retrieval based on full documents.