Towards a Legal Reasoning System based on Description Logics: A Position Paper

Legal reasoning is concerned with various kinds of legal concepts that relate to another concepts used in our daily life. Although those legal concepts are abstract in the sense that there always exist possibilities to interpret them in various ways, lawyers seem to understand them as real things at least in their "legal reality". For instance, Japanese Civil Codes include a notion of falsity that means a false declaration of intention. In spite of its abstractness, well-trained lawyers can judge that one legal act involves the falsity and that the others do not. From this point of view, it seems natural to consider that each legal act has its legal identity. Since the standard first order logic (FOL, for short) is founded on the assumption that every object treated within the logic has its identity, it seems natural to develop a way of representing the legal acts as first-order terms denoting individual objects. However, they are highly related each other at their conceptual level. For instance, a person fills the role of agent in a contract. Thus the two concepts "person" and "contract" are related by the role "agent". Recently in Japan, some researchers [12; 17] try to develop a legal ontology consisting legal concepts and conceptual relationships between them. The latter ones can be roles in description logics. So if we like to build a large legal knowledge base, we would have a description logic containing many legal conceptual terms linked by roles. Based on this, an efficient reasoner (RKB interpreter) would be designed as an extension of FOL prover, for both DL and FOL makes the same assumption that each object has its identity and every concept is a set of objects.