The Omega ontology will provide a semantic framework for the OntoNotes annotation. Each word sense in OntoNotes will be linked to an ontology node in Omega. The parents and siblings of those linked nodes will provide semantic generalizations of the concept conveyed by the word, as well as a place to store additional axioms to help in interpreting the entities and relations conveyed.

Omega is a 120,000-node terminological ontology constructed at USC ISI as the synthesis of WordNet 2.0 (Miller 1990; Fellbaum 1998), a lexically oriented network constructed on general cognitive principles, and Mikrokosmos (Mahesh 1996; O'Hara et al. 1998), a conceptual resource originally conceived to support translation, whose result is subordinated under a new upper model, created expressly in order to facilitate the merging of lower models into a functional whole. Omega, like its close predecessor SENSUS (Knight and Luk 1994), can be characterized as a shallow, lexically oriented, term taxonomy; by far the majority of its concepts can be stated in English using a single word. Omega contains no formal concept definitions and only relatively few interconnections (semantic relations) between concepts. By making few commitments to any specific theories of semantics or particular representations, Omega enjoys a malleability that has allowed it to be used in a variety of applications, including question answering and information integration. A major aim in constructing Omega was to leverage the strengths and minimize the weaknesses of the two major constituents: to have a large, lexically rich resource work with a clear comprehensive organization, supporting both inference and lexical access.

The Omega ontology is being developed at the Information Sciences Institute under the supervision of Prof. Eduard Hovy