Fuzzy set theoretical approach to document retrieval

摘要

The aim of a document retrieval system is to issue documents which contain the information needed by a given user of an information system. The process of retrieving documents in response to a given query is carried out by means of the search patterns of these documents and the query. It is thus clear that the quality of this process, i.e. the pertinence of the information system response to the information need of a given user depends on the degree of accuracy in which document and query contents are represented by their search patterns. It seems obvious that the weighting of descriptors entering document search patterns improves the quality of the document retrieval process.A mathematical apparatus which takes into consideration, in a natural manner, the fact that the grades of importance of the descriptors in document search patterns are of the continuum type, that is an apparatus adequate to the description of a retrieval system of documents indexed by weighted descriptors is—among known mathematical methods—the theory of fuzzy sets, formulated by L.A. Zadeh.It is the aim of this paper to present a new method of document retrieval based on the fundamental operations of the fuzzy set theory. We start by introducing basic notions, then the syntax and semantics of the proposed language for document retrieval will be given and an algorithm allocating documents to particular queries will be described and its properties discussed.The basic advantage of the use of the fuzzy set theory for document retrieval system description is that it takes into consideration, in a simple way, the differentiation of the importance of descriptors in document search patterns and the differentiation of the formal relevance grades of particular documents of an information system to a given query. Documents of the highest grades (in the given information system) of formal relevance to the given query may be retrieved by means of the application of simple operations of the fuzzy set theory.