Fuzzy Induction in Dynamic User Profiling for Information Filtering

In this paper we investigate the role of the user profile in information filtering and we introduce a novel algorithm for learning the user profile based on user’s initial profile and on a queries’ interpretation using fuzzy generalization (Angryk and Petry 2003). Thousands of documents are usually retrieved by search engines for a given query during an information search on WWW. One way to prune irrelevant documents is to take advantage of the user’s implicit interests to filter the documents returned by the search engine, or to reformulate the query based on these interests. One of the common representations of the documents (and queries) in information retrieval is based on the vector hyperspace model (Salton and McGill 1993). We are using the expanded version of Salton’s vector space model introduced by Barbu and Simina (2003) for its effectiveness in computing the dynamics of the user profile. In contrast with the classical vector space model, this recent model, time-words vector hyperspace, has an additional temporal dimension. The coordinates of the documents and queries vectors are calculated using the traditional TF-IDF technique. Only the queries have a temporal dimension (current interest weight) which is set to a preset positive initial value that decays in time, suggesting that some specific user interests could decrease as time goes on. The user’s categories of interest are computed based on a novel approach using Fuzzy Concept Hierarchies (FCH) extracted from the WordNet ontology. An FCH is built for each of the query’s keywords, using their hypernym chains provided by WordNet. A subunitary membership degree (weight) is assigned for each of the edges of the hierarchy via a bottom-up approach, from the lowest level concept (initial keyword) to the more abstract one. The assignment of the weights is performed according to the following two conditions: 1) The sum of weights assigned to the links outgoing from the original keyword has to be equal to unity.