A Visualisation Tool to Explain Case-Base Reasoning Solutions for Tablet Formulation

Case Based Reasoning (CBR) systems solve new problems by reusing solutions of similar past problems. In complex tasks, such as configuration and design, it is not sufficient to merely retrieve and present similar past experiences. This is because the user requires an explanation of the solution in order to judge its validity and identify any deficiencies. Case retrieval with k-nearest neighbour relies heavily on the availability of cases, knowledge about important problem features and the similarity metric. However, much of this information, utilised by the system, is not transparent to the user. Consequently there is a need for tools that can help instil confidence in the system by providing useful explanations to the user. This paper proposes an approach that explains the CBR retrieval process by visualising implicit system design knowledge. This is achieved by visualising the immediate neighbourhood and by highlighting features that contribute to similarity and to differences. The approach is demonstrated on a pharmaceutical tablet formulation problem with a tool called FormuCaseViz. An expert evaluation provides evidence to support our approach.