ABSTRACT
This entry presents a definition of fuzzy set theory and an overview of some applications to model flexible information retrieval systems. The entry focuses on a description of fuzzy indexing procedures defined to represent the varying significance of terms in synthesizing the documents’ contents, the representation of structured documents so as to model a subjective view of document content, the definition of flexible query languages that allow the expression of soft selection conditions, and fuzzy associative retrieval mechanisms to model fuzzy pseudothesauri, fuzzy ontologies, and fuzzy categorizations of documents.
