: Recent studies have pointed out several limitations of expert systems regarding user needs, and have introduced the concepts of cooperation and joint cognitive systems in the focus of AI. While research on explanation generation by expert systems has been widely developed, there has been little consideration of explanation in relation to cooperative systems. Our aim is to elaborate a conceptual framework for studying explanation in cooperation. This work relies heavily on the study of human-human cooperative dialogues. We present our results according to two dimensions, namely, the relation between explanation and problem solving, and the explanation process. Finally, we discuss the implications of these results for the design of cooperative systems. INTRODUCTION Recent studies have pointed out several limitations of expert systems regarding user needs, and have introduced the concepts of cooperation and joint cognitive systems [Woods et al., 1990] in the focus of AI. Our o...

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)....

. 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...

this report was supported by US Defense Advanced Research Projects Agency and monitored by Office of Naval Research, grant no. N00014-96-1-0701. References

In this paper we describe a case study which supports the claim that ontologies are reusable components in the design of knowledge systems. An ontology documents important domain assumptions which would otherwise remain implicit. Whereas a conceptual (or formal) system specification differs between different knowledge systems (even in the same domain), we show the underlying ontology to be invariant. This makes ontologies reusable for knowledge-system design. We illustrate this by discussing how a single legal ontology has been used for the construction of both a planning and an assessment system and argue that the same ontology can be reused for other knowledge systems as well. 1. Reusable components There are important problems in reusing knowledge representations. Building knowledge systems usually entails constructing a new knowledge base from scratch (e.g., [16]). One of the reasons why reusability is impeded is the difficulty in identifying and isolating the reusable components....

To close the gap between knowledge level and symbol level, we present MODEL-K, a language that allows both, to specify KADS conceptual models and to extend them to operational systems. This leads to systems that correctly reflect their underlying conceptual model by retaining structural correspondence between model and implementation. The resulting systems are more perspicuous, easier to communicate and to explain to the user, and better to maintain. Since both, modelling and operationalizing may be interleaved, MODEL-K supports the integration of prototyping in model-based methodologies like KADS as early as possible and on the highest level possible. We illustrate the MODEL-K language with a conceptual model for assignment tasks. We demonstrate how the model, originally developed for the domain of o#ce room allocation, can be reused for an application assigning gates to airplanes 1 . 1 Motivation In the development of knowledge-based systems there is a recognizable sh...