What is Ontology?

A key proposal of my research work was that an ontology is an appropriate way to model context. A common question following from this statement is ”What is ontology?” This is a very good question, as ‘ontology’ refers to a number of things. Before talking about how ontology is used to model context, it is important (and, in my opinion, highly worthwhile) to understand ontology both in its general sense and in the context of the world-wide web.

The word ontology translates as the study of what exists. Ontology can be described as the study of being in so far as this is shared in common by all entities, both material and immaterial. It deals with the most general properties of beings in all their different varieties. As part of metaphysics, ontology is variously concerned with substances, properties, relations, events, times, places and states of affairs. These concepts have readily apparent parallels to the concepts that have been identified in this work as constituting context.

Ontologies are widely used in knowledge-based systems, and are increasingly being applied to web-based systems. In knowledge-based systems, ontologies provide a conceptualisation of a domain of knowledge. This work is interested in being able to express a conceptualisation of context in hypermedia systems.

Ontologies provide a way of modelling the concepts of context in a formal, structured way that is also readily implementable for integration with existing hypermedia systems. Having previously described context as a form of knowledge, I believe it is entirely appropriate to use a knowledge modelling technique to model context. The development of the Ontology Web Language as part of the Semantic Web project provides a way for ontologies to be made available in a form readily consumable by Web applications.