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What is an ontology? What is an upper ontology? Current status of upper ontology? What are some other ontologies around?

An ontology is basically a dictionary for a specific domain, except instead of simply defining terms it defines relationships between the terms and attributes of the terms. AAAI's Ontologies Subtopic has a wonderful explanation of ontology.

An upper ontology attempts to describe concepts that are not specific to any domain by using a hierarchy of entities and rules to unify all domains (without tailoring to a specific one). Determining which items should "exist" in an upper ontology and which shouldn't has become a philosophical argument, dividing the effort and preventing the acceptance of a single upper ontology for all purposes. IEEE's Standard Upper Ontology working group attempts to standardize the effort with its collection of upper ontologies. The first page of What is an Upper Ontology? explains the upper ontology concept further.

The Semantic Web relies upon independently created ontologies to unite terms and concepts across the internet. This way, two independently created pieces of software can communicate, so long as they share common ontologies. For example, when OWL is used to construct a simple SnakeRobot class, it should take advantage of pre-existing robot ontologies much like this:

 <owl:Class rdf:ID="SnakeRobot">
   <rdfs:subClassOf rdf:resource="http://www.cyc.com/2004/06/04/cyc#Robot" />

Use above example in a descriptive example/situation

The Robot term from the Cyc ontology is used in this example, but there are many other RDF and OWL ontologies available in SchemaWeb, the DAML Ontology Library, and Protégé's Sample OWL Ontology list. When searching for a specific term, Swoogle is useful. Also, some of the more popular ontologies are described below.

If you're constructing a new ontology, you may wish to learn more about Ontology building tools

See also