Techniques for ontology visualization

Abstract

Ontology engineering demands clear communication between humans and machines. This process is often impeded by the orientation chasm between their respective language formalisms. This article discusses how to bridge this disconnect by using visual techniques to augment the human comprehension of ontology, which is typically encoded in a machine friendly formalism. Support for ontology visualization comes from research in two interrelated but distinct areas. In ontology visualization techniques (OVT), the focus is on presenting the best visual structure, often interactively, of a targeted ontology for the sake of explorative analysis and comprehension. In visual ontology language (VOL), the focus is on defining the unambiguous, pictorial representation of ontological concepts. Graphs, instead of texts, can then be used in ontology development for the purpose of design, discussion and documentation. There is much contemporary research in the area of OVT, yet the focus directed toward VOL is minimal. By using a fragment of the gene ontology as an example use case, this article surveys the field of OVT by illustrating the different visual effects of various OVT applications. The same gene ontology example is then used to introduce the design and application of a VOL named DLG2, specifically targeted at the RDF-based ontology formalism. The different approach and emphasis between the two types of visual techniques is contrasted.