  Ontologies are one of the core foundations of the Semantic Web. To
participate in Semantic Web projects, domain experts need to be able to
understand the ontologies involved. Visual notations can provide an overview of
the ontology and help users to understand the connections among entities.
However, the users first need to learn the visual notation before they can
interpret it correctly. Controlled natural language representation would be
readable right away and might be preferred in case of complex axioms, however,
the structure of the ontology would remain less apparent. We propose to combine
ontology visualizations with contextual ontology verbalizations of selected
ontology (diagram) elements, displaying controlled natural language (CNL)
explanations of OWL axioms corresponding to the selected visual notation
elements. Thus, the domain experts will benefit from both the high-level
overview provided by the graphical notation and the detailed textual
explanations of particular elements in the diagram.
