About Retrieval Models and Logic

In this paper we investigate some aspects of the logical approach for retrieval models. We develop here the idea that the intrinsic expressive power of logic has already brought its benefits in information retrieval through the design of the first logical retrieval model which has proved more general, or powerful, than any existing model. This benefit lies in the expressive power, or generality of logic on one side, and in its very close fitness with the fundamentals of information retrieval. We mainly develop this second point in giving an informal interpretation of the semantics of the logical model as it was first introduced by C. J. Van Rijsbergen in 1986. This discussion is also for us an occasion to investigate in more details some less known aspects of information retrieval, as for example the impact of new applications which already induce a complete revision of the notion of document. Then the logical model is presented as the one the expressive power of which may provide a much needed common framework for a coherent integration of recent approaches in information retrieval involving the use of Natural Language Processing techniques (NLP) or Artificial Intelligence (AI) techniques. This idea is further developed in showing that the logical approach may also help in giving new insights into classical retrieval models and even help in improving them in a coherent way. An example of this later idea is developed with the Boolean model.