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[protege-owl] Layered Ontologies?

Pitonyak, Andrew D PitonyakA at BATTELLE.ORG
Tue Mar 3 11:00:32 PST 2009

Side note:

The last comment reads as follows:

Interesting connection, Rinke. The term punning appears to describe that reasoning engines can (in a controlled way) prune RDF graphs to ignore certain triples. I have never been a huge fan of the common OWL DL policy to refuse reasoning with any ontology that contains the smallest chunk of OWL Full. Punning is already implemented in several reasoners, e.g. you can use the OWL Full++ ontology that I spoke about in my blog with Pellet (at least via its Jena bridge).

So definitely, a clever punning algorithm could on-the-fly not only ignore the reified relationships, but also add the derived triples, so that the ontology remains meaningful in terms of OWL DL. Rules like the one I described could be used to specify punning rules.

>>> If I understand things correctly, there is no way to use
>>> a class as an individual in OWL2 and there is no way to
>>> just "use" a class as an individual in OWL1 without
>>> making the ontology Full and getting problems with
>>> reasoning.
>> If you intend to use a class as an individual 
>> (ie, the target of an ObjectProperty) then yes, you have OWL Full.

> I am not sure what the implications are for reasoning when
> the ontology becomes OWL full, but I think there are
> severe implications, no?

The primary change when moving from OWL DL to OWL Full is in restrictions on features supported by both, and access to some RDF features. OWL Full allows free mixing of OWL with RDF Schema and, like RDF Schema, does not enforce a strict separation of classes, properties, individuals and data values. OWL DL puts constraints on the mixing with RDF and requires disjointness of classes, properties, individuals and data values. The main reason for having the OWL DL sublanguage is that tool builders have developed powerful reasoning systems which support ontologies constrained by the restrictions required for OWL DL. 

In OWL DL, Datatype properties can not use inverse of, inverse functional, symmetric, or transitive.

OWL DL do not allow cardinality constraints on transitive properties or their inverse, or any super-property.

OWL DL are limited in some instances (I am not sure why).

Much of the RDF and RDFS vocabulary cannot be used in OWL DL.

All classes and properties must be explicitly typed.

OWL DL does not allow properties to link to classes, only individuals.

The constraints are required for OWL DL to fall into the domain of a "Description Logic". In other words, people that study logic and reasoners know that if you stay in OWL DL, then your reasoner is able to make decisions (things are "decidable"). Examples include things like: Is an instance a particular type, checking relations, is a concept a subset of another concept, and is a concept consistent. I expect that consistency is a real problem in OWL FULL.

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