. This paper provides an overview of the OCML modelling language: it illustrates the underlying philosophy, describes the main modelling constructs provided, and compares it to other modelling languages. 1. INTRODUCTION OCML 1 was originally developed in the context of the VITAL project (Shadbolt et al., 1993) to provide operational modelling capabilities for the VITAL workbench (Domingue et al., 1993). Over the years the language has undergone a number of changes and improvements and in what follows we will provide an overview of the current version of the language (v5.1), illustrate its underlying philosophy and compare it to other knowledge modelling languages. 2. LANGUAGE TENETS A number of ideas/principles have shaped the development of the OCML language. These are discussed in the following sections. 2.1. Knowledge-level modelling support. The main goal of OCML is to support knowledge-level modelling (Newell, 1982; Fensel and Van Harmelen, 1994). In practice this role impl...

The IBROW³ project aims to support semi-automatic configuration of intelligent problem solvers out of reusable components. The project takes a holistic approach to reuse and is developing solutions for the various types of technologies required to make reuse both technically and economically feasible. These technologies include innovative software architectures, modelling languages, software libraries, brokering agents and methodologies. In this paper we focus on one particular aspect of the IBROW³ project: the specification of reusable library components. In particular, we illustrate a test case in which a pre-existing library of reusable components for parametric design is reformulated in terms of the framework and constructs provided by the IBROW³ modelling language. The exercise shows the advantages in terms of reusability and usability afforded by the IBROW³ approach. The proposed framework and language provide an effective organization for constructing ...

Much of the work on validation and verification of knowledge based systems (KBSs) has been done in terms of implementation languages (mostly rule-based languages). Recent papers have argued that it is advantageous to do validation and verification in terms of a more abstract and formal specification of the system. However, constructing such formal specifications is a difficult task. This paper proposes the use of formal specification languages for KBS-development that are closely based on the structure of informal knowledge-models. The use of such formal languages has as advantages that (i) we can give strong support for the construction of a formal specification, namely on the basis of the informal description of the system; and (ii) we can use the structural correspondence to verify that the formal specification does indeed capture the informally stated requirements. This paper has been submitted to the Journal of Human Computer Studies (formerly the Journal of Man Machine Studies)....

Abstract. This paper describes the design and implementation of a layered agent architecture for decision support applications in general and for distributed medical care in particular. Three important characteristics which shaped the agent design are identified: distribution of data and control, information uncertainty, and environment dynamism. To provide appropriate decision support in these circumstances the architecture combines a number of AI and agent techniques: a symbolic decision procedure for decision making with incomplete and contradictory information, a concept of accountability for task allocation, commitments and conventions for managing coherent cooperation, and a set of communication primitives for inter-agent interaction. 1.

. To close the gap between knowledge level and symbol level, the MODEL-K language allows to specify KADS conceptual models and to refine them to operational systems. Since both activities may be arbitrarily interleaved, early prototyping is supported at the highest level. Systems written in MODEL-K contain their conceptual model, making them more transparent, easier to communicate to the expert, to explain to the user, and to maintain by the knowledge engineer. The strategy layer of KADS is supposed to control and possibly repair the activities being modeled by the lower layers. MODEL-K views this kind of strategic reasoning as a meta-activity. In the REFLECT project, we came to view meta-activities like resource-management or competence assessment as ordinary problem solving methods, that in turn can be described using KADS. Correspondingly, we extended MODEL-K to model and operationalize such meta-activities. In particular, the lower three layers and the system they mod...

The safety-critical nature of the application of knowledge-based systems to the field of medicine, demands the adoption of reliable engineering principles with a solid foundation for their construction. Logical languages with their inherent, precise notions of consistency, soundness and completeness offer such a foundation, thus promoting scrutinous engineering of medical knowledge. Moreover, logic techniques provide a powerful means for getting insight into the structure and meaning of medical knowledge used in medical problem solving. Unfortunately, logic is currently only used on a small scale for building practical medical knowledge-based systems. In this paper, the various approaches proposed in the literature are reviewed, and related to different types of knowledge and problem solving employed in the medical field. The appropriateness of logic for building medical knowledge-based expert systems is further motivated.

. In this paper we describe a framework for defining and operationalizing conceptual models of distributed knowledge-based systems which extends published approaches by the notion of "agents" and multiple task decompositions. The main part deals with techniques underlying our distributed interpreter. We show how a client-server-architecture can be implemented which allows prototyping distributed knowledge-based systems. Further we describe our mechanism which manages task interactions and supports dependency-directed backtracking efficiently. 1 INTRODUCTION AND OVERVIEW Model-based development of knowledge-based systems is the state of the art in knowledge engineering. A well-known approach in Europe is KADS [14] which allows to model knowledge-based systems on a very high level of abstraction. For this methodology, several formal and/or operational languages were developed [5]. These do not support the distribution of tasks among several agents. Our goal is the development of a frame...

Abstract not found

TFL, the Task Formal Language, has been developed for integrating the static and dynamic aspects of Knowledge Based Systems. This paper focuses on the formal specification of dynamic behaviour. Although fundamental in Knowledge Based System, the strategic reasoning was rather neglected until now by the existing formal specifications. Most languages were generally more focused on the domain and problem-solving knowledge specification than on the control. The formalisation presented here differs from previous ones in several aspects. First, a different representation of dynamic knowledge is proposed : TFL is based on Algebraic Data Types, as opposed to dynamic or temporal logic. Second, dynamic strategic reasoning is emphasised, whereas existing languages only offer to specify algorithmic control. Then, TFL does not only provide the specification of the problem-solving knowledge of the object system, but also of its strategic knowledge. Finally, the dynamic knowledge of the meta-system i...

The literature on validation and verification of knowledge-based systems contains a catalogue of anomalies for knowledge-based systems, such as redundant, contradictory or deficient knowledge. Detecting such anomalies is a method for verifying knowledge-based systems. Unfortunately, the traditional formulation of the anomalies in the literature is very specific to a rule-based knowledge representation, which greatly restricts their applicability. In this paper, we show how the traditional anomalies can be reinterpreted in terms of conceptual models (in particular KADS inference structures). For this purpose, we present a formalisation of KADS inference structures which enables us to apply the traditional rulebase anomalies to these inference structures. This greatly improves the usefulness of the anomalies, since they can now be applied to a much wider class of knowledge-based systems. Besides this reformulation and wider applicability of the traditional anomalies, further contribution...