Fuzzy Rough Set Based Web Query Expansion

Fuzzy rough set theory is a candidate framework for query refinement. Indeed, a thesaurus defines an approximation space in which the query, which is a set of terms, can be approximated from the upper and the lower side. The upper approximation turns out to be too flexible however, resulting in query explosion, while the lower approximation is too strict, resulting in the empty query. Therefore we advocate the use of the lower approximation of the upper approximation, which differs from the upper approximation itself when the thesaurus is not transitive. The resulting technique seems especially useful in the presence of ambiguous query terms.