Legal Knowledge Based System and Legal Education - Focusing on understanding Change of Legal Relation -

It is important for legal education to develop a student’s capability to reason what kind of right and duty relations come to exist as a result of an application of law to a concrete case problem. A legal knowledge base system which logically infers the legal state of affairs as a conclusion from law together with the facts of a case and which clearly shows the reasoning process, is to be a useful tool for legal education. As the legal state of affairs changes according to the time-progress of an event, a clarified logical model of law is necessary to enable us to logically prove changes among legal relationships over time. This study presents such a model based on the concepts of legal sentence as well as their validity and applies it to a contract, i.e. United Nations Convention on Contracts for the International Sale of Goods (CISG) to construct its deductive knowledge base. As a visual representation to represent a legal state of affairs, we have introduced the belt figure of the validity of legal sentences in our legal knowledge base system in order that students can well understand the change in rights and duties relations.