Topic segmentation of message hierarchies for indexing and navigation support.

ABSTRACTMessage hierarchies in web discussion boards grow with new postings. Threads of messages evolve as new postings focus within or diverge from the original themes of the threads. Thus, just by investigating the subject headings or contents of earlier postings in a message thread, one may not be able to guess the contents of the later postings. The resulting navigation problem is further compounded for blind users who need the help of a screen reader program that can provide only a linear representation of the content. We see that, in order to overcome the navigation obstacle for blind as well as sighted users, it is essential to develop techniques that help identify how the content of a discussion board grows through generalizations and specializations of topics. This knowledge can be used in segmenting the content in coherent units and guiding the users through segments relevant to their navigational goals. Our experimental results showed that the segmentation algorithm described in this paper provides up to 80-85% success rate in labeling messages. The algorithm is being deployed in a software system to reduce the navigational load of blind students in accessing web-based electronic course materials; however, we note that the techniques are equally applicable for developing web indexing and summarization tools for users with sight.