A library of problem-solving components based on the integration of the search paradigm with task and method ontologies Enrico Motta and Zdenek Zdrahal Knowledge Media Institute The Open University Walton Hall, Milton Keynes, MK7 6AA, United Kingdom E.Motta, Z.Zdrahal@open.ac.uk Abstract. In this paper we investigate the reuse of tasks and problem solving methods and we propose a model of how to organize a library of reusable components for knowledge based systems. In our approach we first describe a class of problems by means of a task ontology. Then we instantiate a generic model of problem solving as search in terms of the concepts in the task ontology, to derive a task-specific, but method-independent, problem solving model . Individual problem solving methods can then be (re-)constructed from the generic problem solving model through a process of ontology/method specialization and configuration. The resulting library of reusable components enjoys a clear theoretical basis and has been tested successfully on a number of applications. In the paper we illustrate the approach in the area of parametric design. 1. INTRODUCTION A problem solving method (PSM) is a domain-independent specification of the reasoning process of a knowledge-based system (KBS). PSMs play an important role in both the analysis and design phases of the KBS development life-cycle. In particular, they can be used as i) model-based templates to guide the knowledge acquisition (KA) process (van Heijst et al., 1992) and ii) to develop robust and maintainable applications by reuse (Marcus, 1988; Runkel et al., 1996; Motta, 1998b). While all PSMs are obviously designed with some class of problems in mind, it is common to find in the literature a distinction between two main categories of PSMs, which, somewhat ambiguously, are termed task-specific and task-independent. The former are PSMs designed to tackle a particular class of KBS problems - e.g. diagnosis or configuration design - and reflect such a commitment through the use of a problem-specific terminology. Examples of task- specific PSMs include the suite of diagnostic PSMs developed by Benjamins (1993) and the PSMs for design described by Chandrasekaran (1990). Throughout this paper we will use the term problem type (Breuker and van de Velde, 1994) to refer to the high-level generic tasks, e.g. parametric design or fault diagnosis, which are tackled by task-specific PSMs. Task-independent PSMs do not subscribe to a problem-type-specific terminology but specify reasoning steps either in terms of a generic problem solving paradigm, such as search (Newell and Simon, 1976), or in terms of the epistemological properties of the domain knowledge base