Effect of word sets with non-taxonomical relation for retrieval support

At least two kinds of relations exist among related words: the taxonomical relation and the thematic relation. However, although words with a taxonomical relation arc easy to identify from linguistic resources such as dictionaries and thesauri, words with a thematic relation are difficult to identify because they are rarely maintained in linguistic resources. In this paper, we present a method of extracting thematically (nontaxonomically) related word sets among words for retrieval support by employing case-marking articles derived from syntactic analysis. For verifying the capability of such word sets, we compared the results retrieved with words related only taxonomically and those retrieved with words including a word related non-taxonomically to the other words. We found additional term which is thematically related to other terms is effective at retrieving informative pages.