Abstract. To effectively use ontologies on the Web, it is essential that changes in ontologies are managed well. This paper analyzes the topic of ontology versioning in the context of the Web by looking at the characteristics of the version relation between ontologies and at the identification of online ontologies. Then, it describes the design of a web-based system that helps users to manage changes in ontologies. The system helps to keep different versions of web-based ontologies interoperable, by maintaining not only the transformations between ontologies, but also the conceptual relation between concepts in different versions. The system allows ontology engineers to compare versions of ontology and to specify these conceptual relations. For the visualization of differences, it uses an adaptable rule-based mechanism that finds and classifies changes in RDF-based ontologies. The envisaged next generation of the Web (called Semantic Web [6]) will consist of data defined and linked in such a way that it can be used for more effective discovery, automation, integration, and reuse across various applications 3 . In this vision, ontologies have an important role in defining and relating concepts that are used to describe data on the web. However, the distributed and dynamic character of the web will cause that many versions and variants of ontologies will arise. Ontologies are often developed by several persons and continue to evolve over time. Moreover, domain changes, adaptations to different tasks, or changes in the conceptualization might cause modifications of the ontology. This will likely cause incompatibilities in the applications and ontologies that refer to them and will give wrong interpretations to data or make data inaccessible [14] . To form a real Semantic Web, it is necessary that the knowledge that is represented in the different versions of ontologies is interoperable. It is therefore important to create links between ontology versions that specify how the knowledge in the different versions of the ontologies is related. These links can be used to re-interpret data and knowledge under different versions of ontologies.
OntoView REF system helps the user to manage changes in ontologies and keeps ontology versions; it also allows the users to specify conceptual relations between different versions of concepts.
Ontology versioning and change detection on the Web
In 13th International Conference on Knowledge Engineering and Knowledge Management (EKAW02
Computer Science