Information coverage in advisory brokers

Traditionally, information retrieval aims to find information carriers, such as documents, that best match some query or some other (intentional) description of a searcher's information need. In this article, we take the approach that searchers turn to an information retrieval system with the aim of finding several alternatives that completely satisfy their (complex) information need. In other words, searchers expect the retrieval system to help them in covering their information need, rather than merely providing them with a myriad of hopefully relevant information carriers. Ideally, the system should respond by advising one or more packages of information carriers with the requested cumulative effect. This also enables searchers to better trade off between the costs of acquiring and reading/internalizing information carriers versus the expected informational benefits. This article focuses on a theory that aims to clarify the underlying problem area. The theory may consequently be used to enhance information retrieval systems in general and teaching and learning systems in particular, with abilities to better cover a searcher's information need. In the theory presented, we also cater to the fact that searchers may be in different mental moods. The consequence of searchers being in different moods is that information carriers are processed differently. Identifying this influence gives the opportunity to advise users according to their specific moods. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 1155–1188, 2007.