Abstract
Ontologies evolve over time at both structural and semantic levels. Detecting semantic changes to ontologies is essential to the functioning of data instances and dependent ontologies over the semantic Web. In this article, we propose a SemDiff approach to examining structural changes and deriving both explicit and implicit semantic changes between ontology versions. Our approach exploits the semantic dependency between properties and concepts: we introduce the notion of isosems, and conduct implication analysis to examine whether, when, and how semantic changes to an isosem imply semantic changes to other isosems. A prototype of our approach is implemented.