Problem-solving methods provide reusable architectures and components for implementing the reasoning part of knowledge-based systems. The Unified Problem-solving Method description Language UPML has been developed to describe and implement such architectures and components to facilitate their semiautomatic reuse and adaptation. In a nutshell, UPML is a framework for developing knowledge-intensive reasoning systems based on libraries of generic problem-solving components. The paper describes the components and adapters, architectural constraints, development guidelines, and tools provided by UPML. UPML is developed as part of the IBROW project; which provides an internet-based brokering service for reusing problem-solving methods. 1. IBROW started with a preliminary phase under the 4th European Framework and has become a full-fledged Information Society Technologies (IST) project under the 5th European Framework Program since January 2000. Results of its initial phase are described in [

Abstract.We investigate the formal specification of the reasoning process of knowledge-based systems in this paper. We analyze the corresponding parts of the KADS specification languages KARL and (ML) 2 and deduce some general requirements. The essence of these languages is that they integrate a declarative specification of inferences with control information. The languages differ in the way they achieve this integration and each of them has shortcomings. We propose a unifying semantical framework that integrates the core of the different solutions and overcomes their problems. We define a semantics and axiomatization with the Modal Change Logic (MCL). The main contribution of the paper is not to introduce yet another specification language. Instead we aim at four goals: (1) defining a framework for describing the dynamic reasoning behavior of knowledge-based systems which integrates existing approaches; (2) defining a semantics for the specification of the dynamic reasoning behavior of a knowledge-based system within the states as algebras setting that overcomes several shortcomings and ad-hoc solutions of existing approaches; and (3) providing an axiomatization that enables the development of mechanized proof support. (4) Through conceptual and semantical clarity, we investigate the relationships to similar work in software engineering and database engineering opening possibilities for further cross-fertilization of these fields.

The paper introduces a software architecture for the speci®cation and veri®cation of knowledgebased systems combining conceptual and formal techniques. Our focus is component-based speci®cation enabling their reuse. We identify four elements of the speci®cation of a knowledgebased system: a task de®nition, a problem-solving method, a domain model, and an adaptor. We present algebraic speci®cations and a variant of dynamic logic as formal means to specify and verify these dierent elements. As a consequence of our architecture we can decompose the overall speci®cation and veri®cation task of the knowledge-based systems into subtasks. We identify dierent subcomponents for speci®cation and dierent proof obligations for veri®cation. The use of the architecture in speci®cation and veri®cation improves understandability and reduces the eort for both activities. In addition, its decomposition and modularisation enables reuse of components and proofs. Therefore, a knowledge-based system can be built by combining and adapting dierent reusable components.

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