SHYSTER and the calculation of distance between cases

Abstract

The SHYSTER project is concerned with the development of a hybrid legal expert system. The case-based part of SHYSTER chooses the cases upon which to base its opinion by measuring the similarity between previously-decided cases and the case in question. Statisticians make use of many different similarity measures, however – for SHYSTER - each of the commonly used similarity measures reduces to one of three measures. These measures can be weighted so that some facts in the cases can be given more importance than others. SHYSTER uses one of these weighted measures (a distance measure) to construct it opinion. Early testing shows that SHYSTER's approach to finding the distance between cases allows it to produce useful advice. Further testing will attempt to validate this approach empirically.