OWL

Ontology Web Language

•  http://en.wikipedia.org/wiki/Web_Ontology_Language
•  OWL 2
•  guide
•  Protege OWL tutorial

OWL use cases

Modeling

Ontologies are created to fix terms in their meaning. So that confusion about their definition is avoided. Many ontologies are written in the OBO format an easily human readable text format. For example GO is defined in OBO. OWL is a more formal definition of an Ontology. This gives it a lot of powerful features that one can use. While also incurring a steep learning curve.

Reasoning

OWL allows reasoning over statement using description logic. That means that one does not need to encode all implied information in your system to be able to get conclusive data.

e.g. jenny a :woman jenny :hasMother mum; mum a :mother;

In a classical system without reasoning when asking the question select ?s where {?p rdf:Type :woman}; will only answer jenny. After adding the following OWL axiom. :mother owl:subClassOf :woman

The answer would become jenny and mum. As the axiom leads to the inference that mum is a :Woman. So the new triple mum a :woman

Constraint Validation

Lets add a simple constraint too the Ontology. Being rather conservative. :man owl:disjointWith :woman

That means if we had made a mistake filling our triple store and we had added a. mum a :man our OWL logic would raise a contradiction.

A product meant for this is  http://clarkparsia.com/pellet/icv