document: Topic segmentation of message hierarchies for indexing and navigation support Message 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 .
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