Information retrieval systems: where is the fuzz?

If the field of fuzzy information systems is to grow and mature, it is imperative to define terms precisely. For the sub-field of information retrieval, we attempt to clarify the definition of some terms and discuss the possible sources of fuzziness within this sub-field. Moreover, we discuss the implications that this has in terms of defining flexible information retrieval models and propose an approach to information retrieval in the framework of possibility theory.