Web Ontology Language (OWL)

OWL

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

Why not be inconsistent in at least one aspect of a language which is all about consistency?

—Guus Schreiber, Why OWL and not WOL?

the acronym OWL was proposed … as an easily pronounced acronym that would yield good logos, suggest wisdom ...

OWL

What is Ontology? Ontology is about the exact description of things and

their relationships.

For the web, ontology is about the exact description of web information and relationships between web information.

OWL is built on top of Resource Description Framework (RDF)

OWL is written in XML OWL has three sub languages

OWL lite OWL DL OWL Full

Semantic Web

Information is given explicit meaning XML provides a surface syntax for structured

documents, but imposes no semantic constraints on the meaning of these documents.

XML Schema is a language for restricting the structure of XML documents and also extends XML with datatypes.

Semantic Web

RDF is a datamodel for objects ("resources") and relations between them, provides a simple semantics for this datamodel, and these datamodels can be represented in an XML syntax.

RDF Schema is a vocabulary for describing properties and classes of RDF resources, with a semantics for generalization-hierarchies of such properties and classes.

Semantic Web

OWL adds more vocabulary for describing properties and classes: among others, relations between classes (e.g. disjointness), cardinality (e.g. "exactly one"), equality, richer typing of properties, characteristics of properties (e.g. symmetry), and enumerated classes.

Semantic Web

Information has meaning This information can be processed by computers Computers can use this information for many

purposes

example

An ontology describing families might include axioms stating that a "hasMother" property is only present between two individuals when "hasParent" is also present, and individuals of class "HasTypeOBlood" are never related via "hasParent" to members of the "HasTypeABBlood" class. If it is stated that the individual Harriet is related via "hasMother" to the individual Sue, and that Harriet is a member of the "HasTypeOBlood" class, then it can be inferred that Sue is not a member of "HasTypeABBlood".

example

<owl:Class rdf:ID="Wine"> <rdfs:subClassOf rdf:resource="&food;PotableLiquid"/> <rdfs:subClassOf> <owl:Restriction> <owl:onProperty rdf:resource="#madeFromGrape"/> <owl:minCardinality rdf:datatype="&xsd;nonNegativeInteger">1</owl:minCardinality> </owl:Restriction> </rdfs:subClassOf> ... </owl:Class>

Citations

Patel-Schneider, P. F. (2004, June). What is OWL (and why should I care)?. In KR (pp. 735-737).

http://www.w3.org/2001/sw/wiki/OWL

http://www.w3.org/TR/owl-features/