Web Ontology Language
The W3C Web Ontology Language (OWL) is a Semantic Web language designed to represent rich and complex knowledge about things, groups of things, and relations between things.
OWL is a computational logic-based language such that knowledge expressed in OWL can be exploited by computer programs, e.g., to verify the consistency of that knowledge or to make implicit knowledge explicit.
OWL documents, known as ontologies, can be published in the World Wide Web and may refer to or be referred from other OWL ontologies.
The current version is OWL 2.
Link between RDF and OWL
The first class in OWL is Owl:Thing Class.
The currently most widely used OWL editor is Protégé, a free open-source editing framework developed at Stanford University.
Other editors are TopQuadrant's commercial TopBraid Composer and the open-source systems SWOOP and NeOn-Toolkit.
An example of how to use such an editor, like Topbraid Composer, with Coins is explained in the OWL and Coins sample.