Abstract. Ontologies are now used within an increasing number of realworld applications. So far, significant effort has been spend in building tools to support users in creating, maintaining, and browsing the terminological part of an ontology. On the other hand, only little work has been done in supporting the user to explore the manifold interconnected assertional knowledge in order to analyze, visualize, and understand this network of individuals. In this paper, we present a new efficient visualization and editing approach which allows to investigate relationships within large volumes of interlinked individuals in order to grasp the structure of the assertional knowledge more easily. 1 Motivation An OWL ontology typically consists of two parts [2]: The terminological or schema part introduces concepts and properties and gives structure to them in terms of axioms using the available OWL Lite or OWL DL language constructs (also called TBox in Description Logics). The assertional or ...