Plexus-the expert system for referral

Abstract PLEXUS is an expert system which is designed as a referral tool to be used in public libraries. It was developed by the Central Information Service (CIS) at the University of London under a grant awarded by the British Library Research and Development Department. The first phase, which resulted in a working prototype, was completed in 20 months. A second phase, also funded by the British Library, is now under way and will involve the testing, evaluation, and further development of the prototype. The system should be able to carry out the same kind of tasks as the human reference librarian does and should do it in a way which, if done by a human would be described as intelligent. The system should be able to obtain a description of the user's problem and, if necessary, to supplement the user's original statement either by deriving additional concepts or by asking the user to answer some questions. The problem description should then be transformed into a search strategy that could be applied to a data base or referral resources. The results of a search should be evaluated both by the system and the user. Should the initial search strategy produce unsatisfactory results, the system should infer an appropriate action. The search strategy would be gradually reformulated until a satisfactory outcome was achieved. The result of the search should then be presented to the user. The prototype system is restricted to gardening because it was assumed that it would be of general appeal to the users of a public library. The paper describes the knowledge base of PLEXUS, its representation, the control mechanism, and the working system as a whole.