A language modeling approach to question answering on speech transcripts

This paper presents a language modeling approach to sentence retrieval for Question Answering (QA) that we used in Question Answering on speech transcripts (QAst), a pilot task at the Cross Language Evaluation Forum (CLEF) evaluations 2007. A language model (LM) is generated for each sentence and these models are combined with document LMs to take advantage of contextual information. A query expansion technique using class models is proposed and included in our framework. Finally, our method´s impact on exact answer extraction is evaluated. We show that combining sentence LMs with document LMs significantly improves sentence retrieval performance, and that this sentence retrieval approach leads to better answer extraction performance.