Z-BASED FORMALIZATION OF KITS OF CHANGES TO MAINTAIN ONTOLOGY CONSISTENCY Najla Sassi, Wassim Jaziri and Faiez Gargouri Higher Institute of Informatics and Multimedia, Sfax University, Tunisia Keywords: Changing Environment, Ontology, Coherence, Kits of Change, Z language. Abstract: In changing environments, supporting ontology’s evolution is essential to integrate changes and to manage ontology versions. It is also important to guarantee the consistency of ontology when changes occur. In this paper, we present an ontology evolution approach based on kits of changes. These kits are based on changes operators and additional changes which correct inconsistencies caused by the changes operators. A formalization of the kits of changes is also proposed based on the Z language. 1 INTRODUCTION Ontology is an explicit representation of knowledge related to a domain of study and a particular context. The application of changes in its conceptual entities is a modification of a subset of knowledge represented by the ontology. The application of changes requires defining the mechanisms specifying how knowledge can be changed and how to maintain the consistency of knowledge after each change. Ontology evolution is the process of adaptation of ontology to evolution changes and the consistent management of these changes to guarantee the consistency of ontology when changes occur (Klein et al., 2001) (Noy et al., 2004). It encompasses the set of activities, both technical and managerial, which ensures that ontology continues to meet organizational objectives and users needs in an efficient and effective way (Stojanovic, 2004). The adaptation of ontology to evolution changes is a complex process from which several problems must be managed: identification of evolution changes, analysis of effects of changes, management of the ontology consistency, storage of ontology versions, etc. We are especially interested in this paper at defining kits of changes to update, in a coherent way, the ontology to new evolution requirements. This paper is organized as follows: Section 2 presents the evolution approach based on kits of changes. In section 3, we specify the kits of changes using pre-conditions, post-conditions, potential inconsistencies and additional changes. Section 4 defines a formalization of the ontology structure based on the ontology meta-model. The formal specification of kits of changes using Z language is presented in section 5 before concluding in section 6. 2 KITS OF CHANGES In changing contexts, the management of changes and the maintaining of the ontology consistency require analyzing and identifying effects of changes on all ontology elements as well as defining additional operations to correct inconsistencies. In our approach, we express the requirements of ontology evolution using types of changes. Indeed, the evolution of ontology is the update of one or more ontological entities. To allow updating an ontological entity, we define primitive and composite operators called types of changes able to evolve ontology. These types of changes extend these proposed in the literature (Klein et al., 2002) (Stojanovic, 2004) to express all evolution possibilities on the ontological entities: concepts, relationships, properties and axioms (Sassi et al., 2008). However, types of changes ensure only the modification of ontology. They not guarantee that ontology remains coherent after modifications. The definition of types of changes must be associated with adequate mechanisms to ensure the consistency 388 Sassi N., Jaziri W. and Gargouri F. (2009). Z-BASED FORMALIZATION OF KITS OF CHANGES TO MAINTAIN ONTOLOGY CONSISTENCY. In Proceedings of the International Conference on Knowledge Engineering and Ontology Development, pages 388-391 Copyright c  SciTePress