Representation of knowledge in a legal information retrieval system

Recent interest in computer representation of knowledge has led to the development of 'expert' computer assistants for tasks such as medicaldiagnosis, technical instruction, and problem solving in restricted domains (Brown and Burton, 1975; Davis, Buchanan and Shortliffe, 1977; Goldstein and Roberts, 1977). Each of these systems is based on a semantic model of a specific subject area, along with some general methods for using subject area knowledge to understand and respond to users' requests. The emphasis of these systems is not on 'solving' problems by computer, but rather on helping a human problem solver organise and apply a complex body of knowledge. The research described here explores the use of subject area knowledge in an 'expert' document retrieval system. The goals of the research are to characterise the semantics of information retrieval requests, and to develop methods for representing and using subject area knowledge in computer retrieval systems. The Legal Research System (LRS) is a knowledge-based computer retrieval system, intended to be used by lawyers and legal assistants to retrieve information about court decisions (cases) and laws passed by legislatures (statutes). The subject of its knowledge is Negotiable Instruments Law, an area of Commerical Law that deals with cheques and promissory notes (White and Summers, 1972; Speidel, Summers and White, 1974). The current implementation of the system (Hafner, 1978) has a database of about 200 statutes from the Uniform Commerical Code (American Law Institute, 1972) and 200 related cases. In LRS four kinds of knowledge about legal concepts and relationships are represented: functional knowledge, structural knowledge, semantic knowledge and factual knowledge. In this chapter the motivation for including each kind of knowledge is discussed, the computer representation of each kind of knowledge is described and examples of the use of each kind of knowledge in LRS are presented. The next section gives a very brief overview of current legal retrieval systems, both manual and automated. Subsequent sections describe the representation of knowledge in LRS, and the use of this knowledge to understand and interpret user queries.