Subtopic Structuring fbr l?ull-Length Document Access

We argue that the advent of large volumes (of fulllength text, as opposed to short texts like abstracts and newswire, should be accompanied by corresponding new approaches to information access. Towamd this end, we discuss the merits of imposing structure on fulllength text documents; that is, a partition of t’he text into coherent multi-paragraph units that represent the pattern of subtopics that comprise the text. Using this structure, we can make a distinction between the main topics, which occur throughout the length of the text, and the subtopics, which are of only limited extent. We discuss why recognition of subtopic structure is important and how, to some degree of accuracy, it can be found. We describe a new way of specifying queries on full-length documents and then describe an experiment in which making use of the recognition of local structure achieves better results on a typical information retrieval task than does a standard IR measure.