Legislation as Logic Programs

The linguistic style in which legislation is normally written has many similarities with the language of logic programming. However, examples of legal language taken from the British Nationality Act 1981, the University of Michigan lease termination clause, and the London Underground emergency notice suggest several ways in which the basic model of logic programming could usefully be extended. These extensions include the introduction of types, relative clauses, both ordinary negation and negation by failure, integrity constraints, metalevel reasoning and procedural notation. In addition to the resemblance between legislation and programs, the law has other important similarities with computing. It needs for example to validate legislation against social and political specifications, and it needs to organise, develop, maintain and reuse large and complex bodies of legal codes and procedures. Such parallels between computing and law suggest that it might be possible to transfer useful results and techniques in both directions between these different fields. One possibility explored in this paper is that the linguistic structures of an appropriately extended logic programming language might indicate ways in which the language of legislation itself could be made simpler and clearer.