The notion of relevance (I)

Analysis of the problems of defining the mutual relevancies of queries and document‐collections indicates that they essentially involve the problem of conceptual relatedness. In order to consider the latter problem, the question of concept‐formation is first discussed, which in turn requires a definition of concept. An extensional interpretation is suggested whereby a concept is associated with a class of conceptually‐similar documents. Users' similarity‐judgments then provide the empirical data for formal definitions of concept and conceptual relatedness. It is found, however, that certain very general difficulties rule out the possibility of defining concepts and their relatedness by the method proposed. Since this method is based on human relevance‐judgments, it seems a natural one to adopt, so that its collapse has serious practical and theoretical consequences. An alternative approach is therefore proposed whose elaboration will form Part II of this article.