BUILDING EXPLANATIONS FROM RULES AND STRUCTURED CASES

A central task underlying many of the activities of attorneys is inferring the legal consequences of a given set of facts. GREBE (GeneratoR of Exemplar-Based Explanations) is a system that uses detailed knowledge of the facts and reasoning of specific past cases, together with legal rules and common-sense knowledge, to determine and justify the legal consequences of new cases. GREBE can apply either rule-based reasoning or case-based reasoning to goals at any level of its analysis. GREBE uses an approach to case-based reasoning in which new cases are compared with the smallest collections of precedent facts that justified an individual inference step in the explanation of a precedent case. This enables knowledge of the interactions among individual inference steps in a precedent to be used in case comparison. Case comparison is also assisted by an expressive semantic network representation of case facts. Techniques are presented for retrieving and comparing cases represented in this formalism. GREBE's output is a memorandum that justifies a legal conclusion in terms of the applicable precedents and legal rules. © 1991.