Thesaurus and Query Expansion

The explosive growth of the World Wide Web is making it difficult for a user to locate information that is relevant to his/her interest. Though existing search engines work well to a certain extent but they still face problems like word mismatch which arises because the majority of information retrieval systems compare query and document terms on lexical level rather than on semantic level and short query: the average length of queries by the user is less than two words. Short queries and the incompatibility between the terms in user queries and documents strongly affect the retrieval of relevant document. Query expansion has long been suggested as a technique to increase the effectiveness of the information retrieval. Query expansion is the process of supplementing additional terms or phrases to the original query to improve the retrieval performance. The central problem of query expansion is the selection of the expansion terms based on which user's original query is expanded. Thesaurus helps to solve this problem. Thesaurus have frequently been incorporated in information retrieval system for identifying the synonymous expressions and linguistic entities that are semantically similar. Thesaurus has been widely used in many applications, including information retrieval and natural language processing.