Discourse-based answering of why-questions

This paper presents the work that we have carried out in investigating the purpose of discourse structure for why-question answering (why-QA). We developed a system for answering <em>why</em>-questions that employs the discourse relations in a pre-annotated document collection (the RST Treebank). With this method, we obtain a recall of 53.3% with a mean reciprocal rank (MRR) of 0.662. We argue that the maximum recall that can be obtained from the use of RST relations as proposed in the present paper is 58.0%. If we discard the questions that require world knowledge, maximum recall is 73.9%. We conclude that discourse structure can play an important role in complex question answering, but that more forms of linguistic processing are needed for increasing recall.