TRACS: A SUPPORT TOOL FOR DRAFTING AND TESTING LAW
Nienke den Haan · 1991
Summary This paper discusses the results of the implementation of a prototype system for the application of traffic law. The problems tackled in this system are the computational complexity of legal reasoning regarding the use of knowledge about the world, and the representation and reasoning with deontic modalities. Testing two paragraphs already rendered several important notes about the design of the traffic law. This paper reveals the experiences and results, and gives directions for further research. In the winter of 1991 the TRACS project was started. It was supported by a grant of the Dutch Association for Scientific Research into Traffic Safety (SWOV). Initially, the project aimed at the construction of an intelligent teaching system (ITS) for law. However, since the SWOV is also concerned with testing new versions of the traffic law as presented to them by the Ministry of Transport and Public Works, the application of law became the core interest. This explains the TRACS acronym: Traffic Regulation Application and Comparison System. Applying law is the basis both for legal ITS and for testing law. The design of the system was presented in [Den Haan & Breuker, 1991]. The prototype, which was programmed to perform the elementary legal-reasoning processes involved in law application, proved to have important results. The actual application of law is the core activity of legal reasoning. An other important issue is the analysis of facts and the interpretation of vague terms. Not being the goal of our research, they have not been embedded in the system. The TRACS project aims at regulation-based reasoning and embodies the application of the traffic law. The legimitization of the results is considered to be a task that, in our opinion, requires thorough legal experience and up to date knowledge of the social structure. The implementation of the system has proceeded as planned in the presented design. The next section will recapitulate this design, in order to provide a framework for the discussion of the results. Section 3 reflects on the representation formalism used in the prototype. Subsequently, section 4 elaborates on the tests, and section 5 shows what implications for law drafting have surfaced. 2. TRACS design The short term goal for the functionality of TRACS is the application of law. The legal reasoning of TRACS involves the search for applicable rules and the selection of rules with the highest priority. The three layers of legal reasoning (application, selection and validation) are clearly visible in figure 1. In short, rules are found applicable if facts in the situation description can be matched to the grounds for rule application, as stated in the condition parts of rules. Priority rules are used to determine an order in the set of applicable rules. For each law text, specific priority rules can be found, sometimes stated in the text itself. Additional general priority rules are defined for the entire law domain. The validation process is quite similar to the application process, but matches the conclusions of rules to the situation description.