Reasoning in ontologies and knowledge bases is one of the reasons why a specification needs to be formal one. By reasoning we mean deriving facts that are not expressed in ontology or in knowledge base explicitly. Reasoners are used to reason the ontology.
Tasks of Ontology Reasoners
A few examples of tasks required from reasoner are as follows.
- Satisfiability of a concept - determine whether a description of the concept is not contradictory, i.e., whether an individual can exist that would be instance of the concept.
- Subsumption of concepts - determine whether concept C subsumes concept D, i.e., whether description of C is more general than the description of D.
- Consistency of ABox with respect to TBox - determine whether individuals in ABox do not violate descriptions and axioms described by TBox.
- Check an individual - check whether the individual is an instance of a concept
- Retrieval of individuals - find all individuals that are instances of a concept
- Realization of an individual - find all concepts which the individual belongs to, especially the most specific ones
OWL Reasoners
A reasoner is a key component for working with OWL ontologies. In fact, virtually all querying of an OWL ontology (and its imports closure) should be done using a reasoner. This is because knowledge in an ontology might not be explicit and a reasoner is required to deduce implicit knowledge so that the correct query results are obtained. The OWL API includes various interfaces for accessing OWL reasoners. In order to access a reasoner via the API a reasoner implementation is needed. There following reasoners (in alphabetical order) provide implementations of the OWL API OWLReasoner interface:
- FaCT++.
- HermiT
- Pellet
- RacerPro
0 comments:
Post a Comment