We present an application of metaprogramming in logic that, unlike most metaprogramming applications, is not primarily concerned with controlling the execution of logic programs. Metalevel computation is used to define theories from schemata that were either given explicitly or obtained by abstraction from other theories. Our main application is a representation of legal knowledge in a metalogic programming language. We argue that legal knowledge is multilayered and therefore a single level representation language lacks the needed expressiveness. We show that legal rules can be partitioned into primary, secondary, tertiary, quaternary, and higher level rules. Our classification enables us to define a multilevel model of legal knowledge and a one-to-one correspondence with levels of metaprogramming in logic. We show that this framework has a potential for capturing important legal interpretation principles such as analogia legis, lex specialis Zegi generuli derogut, etc. We have a running example from commercial law that utilizes rules up to the tertiary level, emphasizing unulogiu legis. The example is expressed in a multilevel metalogic programming language that provides a naming convention and employs reflection between levels.

A representation methodology for knowledge allowing multiple interpretations is described. It is based on the following conception of legal knowledge and its open texture. Since indeterminate, legal knowledge must be adapted to fit the circumstances of the cases to which it is applied. Whether a certain adaptation is lawful or not is measured by metaknowledge. But as this too is indeterminate, its adaptation to the case must be measured by metametaknowledge, etc. This hierarchical model of law is quite wellestablished and may serve well as a basis for a legal knowledge system. To account for the indeterminacy of law such a system should support the construction of different arguments for and against various interpretations of legal sources. However, automatizing this reasoning fully is unsound since it would imply a restriction to arguments defending interpretations anticipated at programming time. Therefore, the system must be interactive and the user's knowledge be furnished in a principled way. Contrary to the widespread opinion that classical logic is inadequate for representing open-textured knowledge, the framework outlined herein is given a formalization in first order logic.

We propose an architecture for building expert systems in which the main subsystems are distinct but communicating programs: a Prolog inference engine, a multimedia interface tool and a data base management system. We have used this architecture for constructing a legal expert system for labour law. We propose a novel approach for capturing vague concepts. The vagueness is not represented in the sense that its extent is quantified but instead rules are given for evaluating the concept in a given situation. The method is analogous to legal practice; lawyers develop methods for judging whether vague concepts apply to fact situations. These methods are used for identifying the relevant subquestions and legal text documents for analyzing the case in issue. Our system reflects this and other aspects of a lawyer's practical work. This paper was presented at DEXA '90, the International Conference on Data Base and Expert Systems Applications, on 29--31 August 1990 in Vienna, Austria. This rese...

Formalization presupposes 'precisification'. A formal representation, therefore, cannot account for all relevant aspects of imprecise domain knowledge. In this