Ontologies, OWL, taxonomies and classifications

Ontologies

An ontology is a vocabulary used to describe some domain. This includes describing the entities in the domain, and their relationships.

OWL

The Web Ontology Language (OWL) is a W3C endorsed format that can be used to define an ontology. It can define relatively rich semantics including relations between classes of entities (for example disjointness), cardinality (for example "exactly one"), equality, properties, characteristics of properties (for example symmetry), and enumerated classes.

Taxonomies

At a more simplistic level, OWL can also describe taxonomies. A taxonomy is a system of hierarchical types that can be used to describe entities. The types are expressed in a class and subclass system.

So for example, a basic taxonomy might consist of a class called "Transport" which might have subclasses "Air Transport" and "Land Transport". Then, "Land Transport" might in turn have subclasses "Bus" and "Car". This hierarchy means that a "Car" is a type of "Land Transport", and is also a type of "Transport".

Classifications

WSRR is able to load and understand OWL files, but currently does not exploit all the features of the OWL language. Instead, the taxonomy part of the OWL file is made available to "classify" artifacts in WSRR. In the WSRR web UI, each taxonomy is referred to as a "classification system", and the classes in the taxonomy are referred to as "classifications" or "classification classes".