A formal analysis of the problem of parametric design is given on the basis of the competence-theory approach to problem solving methods. In particular, the ontological commitments and assumptions underlying some problem solving methods as used in the VT task are investigated.

This paper describes how we applied the PROTG-II architecture to build a knowledgebased system that configures elevators. The elevator-configuration task was solved originally with a system that employed the propose-and-revise problem-solving method (VT; Marcus, Stout & McDermott, 1988). A variant of this task, here named the Sisyphus-2 problem, is used by the knowledge-acquisition community for comparative studies. PROTG-II is a knowledge-engineering environment that focuses on the use of reusable ontologies and problem-solving methods to generate task-specific knowledge-acquisition tools and executable problem solvers. The main goal of this paper is to describe in detail how we used PROTG-II to model the elevator-configuration task. This description provides a starting point for comparison with other frameworks that use abstract problem-solving methods. Starting from a detailed description of the elevator-configuration knowledge (Yost, 1992), we analyzed the domain knowledge and developed a general, reusable domain ontology. We selected, from PROTG-II's library of preexisting methods, a propose-and-revise method based on chronological backtracking. We then configured this method to solve the elevator-configuration task in a knowledge-based system named ELVIS. We entered domain-specific knowledge about elevator configuration into the knowledge base with the help of a task-specific knowledge-acquisition tool that was generated from the ontologies. After we constructed mapping relations to connect the domain and method ontologies, PROTG-II generated the executable problem solver. We have found that the development of ELVIS has provided a valuable test case for evaluating PROTG-II's suite of system-building tools.

Situated cognition is not a mere philosophical concern: it has pragmatic implications for current practice in knowledge acquisition. Tools must move from being design-focused to being maintenance-focused. Reuse-based approaches (e.g. using problem solving methods) will fail unless the reused descriptions can be extensively modified to suit the new situation. Knowledge engineers must model not only descriptions of expert knowledge, but also the environment in which a knowledge base will perform. Descriptions of knowledge must be constantly re-evaluated. This re-evaluation process has implications for assessing representations 1.

The knowledge-engineering literature contains a number of approaches for constructing or selecting problem solvers. Some of these approaches are based on indexing and selecting a problem solver from a library, others are based on a knowledge acquisition process, or are based on searchstrategies. None of these approaches sees constructing a problem solver as a configuration task that could be solved with an appropriate configuration method. We introduce a representation of the functionality of problem solving methods that allows us to view the construction of problem solvers as a configuration problem, and specifically as a parametric design problem. From the available methods for parametric design, we use propose-critique-modify for the automated configuration of problem solving methods. We illustrate this approach by a scenario in a small car domain example. 1 Introduction The literature on Knowledge Engineering has identified a number of different problem types, HayesRoth, Waterman,...

This paper describes the PROTEGE-II environment which supports the construction of knowledge-base systems from reusable compo-nents. To assist developers with reuse, the terminologies of both problem-solving methods and knowledge bases should be described as formal ontologies. To connect pre-existing methods to new domains and knowledge bases, we dejine declarative mapping relations, which we use to translate information from domains to methods. It is critical that these mappings are simple, and we develop an ontology and a tool to constrain their construction. With PROTEGE-II and a set of mapping relations, we are able to reuse the same problem-solving method with two disparate tasks: (1) configuring the parts of an elevator system and (2) identzfling plausible con.gurations of helices in a ribosome molecular strand. 1. Reuse for Knowledge-Based Systems Software reuse is an appealing solution to the high cost

. Knowledge-based configuration is both a successful application domain for AI techniques and and an active research area. An open issue in many practical domains is that of reconfiguration, typically exhibited by legacy systems that are to be extended, upgraded or simply altered. Standard configuration techniques are not necessarily suited to this task. We discuss the use of a diagnosis approach to reconfiguration. We present the differing application and representation requirements, develop a representation that is suitable for expressing the information about the required and configurable functionalities from the diagnosis point of view, present an example and discuss our experiences. 1. Introduction The automated configuration of technical systems is a successful application area for knowledge-based techniques. Initially, configuration research followed the mainstream of expert system research with the use of rule-based expert systems for configuration purposes (McD82), and rule-...

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Explanation is an important issue in building computer-based interactive design environments in which a human designer and a knowledge system may cooperatively solve a design problem. We consider the two related problems of explaining the system's reasoning and the design generated by the system. In particular, we analyze the content of explanations of design reasoning and design solutions in the domain of physical devices. We describe two complementary languages: task-method-knowledge models for explaining design reasoning, and structure-behavior-function models for explaining device designs. INTERACTIVE KRITIK is a computer program that uses these representations to visually illustrate the system's reasoning and the result of a design episode. The explanation of design reasoning in INTERACTIVE KRITIK is in the context of the evolving design solution, and, similarly, the explanation of the design solution is in the context of the design reasoning.

Original version submitted to the publisher. An elevator configuration task, the VT task, is modelled within DESIRE as a design task. DESIRE is a framework within which complex reasoning tasks are modelled as compositional architectures. Compositional architectures are based on a task decomposition, acquired during task analysis. An earlier developed generic task model of design, based on a logical analysis and synthesis of task models devised for diverse applications, has been refined for the elevator configuration task. The resulting task model includes a description of the ontology of the elevator domain and a description of the task model. 1.

. 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 ...