Does Pellet reason with OWL-Full ontologies?
OWL-DL restricts OWL-Full ontologies in several different ways as explained in Section 8.2 of OWL reference. Pellet relaxes most of the OWL-DL restrictions and handles OWL-Full ontologies (see the list below for more details).
Any OWL-Full feature that is not supported by the reasoner will be ignored. When an OWL-Full ontology is loaded to the reasoner, a series of warning messages will be printed about the axioms violating the OWL-DL restrictions. This behavior can be changed such that Pellet will refuse to load the OWL-Full ontology by throwing an exception. This can be achieved by setting the configuration option IGNORE_UNSUPPORTED_AXIOMS to false.
The following list contains all the OWL-DL restrictions defined in the OWL specification and for each restriction explains if/how Pellet relaxes that restriction:
- OWL-DL Restriction: OWL-DL requires a pairwise separation between classes, datatypes, datatype properties, object properties, annotation properties, ontology properties (i.e., the import and versioning stuff), individuals, data values and the built-in vocabulary. This means that, for example, a class cannot be at the same time an individual.
Pellet Restriction: Pellet uses punning semantics of OWL 1.1 to partially overcome the vocabulary separation restriction. The punning support in Pellet is explained here.
- OWL-DL Restriction: In OWL-DL the set of object properties and datatype properties are disjoint. This implies that the following four property characteristics:
o inverse of,
o inverse functional,
o symmetric, and
o transitive
can never be specified for datatype properties.
Pellet Restriction: Pellet has these restrictions with the exception of inverse functional datatype properties. Pellet fully supports inverse functional datatype properties. Axioms violating other restrictions are ignored.
- OWL-DL Restriction: OWL DL requires that no cardinality constraints (local nor global) can be placed on transitive properties or their inverses or any of their superproperties.
Pellet Restriction: Pellet requires this restriction. Any transitivity axiom violating these restrictions are ignored (cardinality restrictions are not ignored).
- OWL-DL Restriction: Annotations are allowed only under certain conditions. See Sec. 7.1 for details.
Pellet Restriction: Annotations have no effect on reasoning results and will be completely ignored by Pellet regardless of the configuration option.
- OWL-DL Restriction: Most RDF vocabulary cannot be used within OWL DL. See the OWL Semantics and Abstract Syntax document [OWL S&AS] for details.
Pellet Restriction: Pellet relaxes this restriction by extending punning to built-in RDFS vocabulary. For example, if rdf:List is used in individual assertions it will be treated as a new class.
- OWL-DL Restriction: All axioms must be well-formed, with no missing or extra components, and must form a tree-like structure. This constraint implies that all classes and properties that one refers to are explicitly typed as OWL classes or properties, respectively.
Pellet Restriction: Pellet partially requires this restriction. All axioms need to be well-formed and any other axiom will be ignored. However, some URI’s might be untyped and Pellet will uses some heuristics to infer the type for those URI’s. For example, if a URI is used in a owl:subClassOf then that URI will be treated as if it is defined as an OWL class.
- OWL-DL Restriction: Axioms (facts) about individual equality and difference must be about named individuals.
Pellet Restriction: Pellet requires this restriction. If one uses owl:sameAs or owl:differentFrom on URI’s that are not defined as individuals, Pellet will use punning to infer that same URI’s are also used as individuals.
