FullDifferencesSpecIntro

From OWL
Jump to: navigation, search

Discussion of the introductory parts of the OWL-Full spec.

The following text is copied&pasted from the OWL-Full spec.

The introduction of the OWL-Full spec

5. RDF-Compatible Model-Theoretic Semantics (Normative)
=======================================================
This model-theoretic semantics for OWL is an extension 
of the semantics defined in the RDF semantics [RDF Semantics], 
and defines the OWL semantic extension of RDF.
Review comment from m_schnei 09:22, 21 March 2008 (EDT)
The two hyperlinks to "RDF semantics" and to "semantic extention" point to an outdated working draft of the RDF semantics spec.
NOTE: There is a strong correspondence between 
the semantics for OWL DL defined in this section 
and the Direct Model-Theoretic Semantics defined in Section 3 
(see Theorem 1 and Theorem 2 in Section 5.4). 
If, however, any conflict should ever arise 
between these two forms, then the Direct Model-Theoretic Semantics 
takes precedence.
Review comment from m_schnei 09:24, 21 March 2008 (EDT)
This paragraph will become obsolete, if the DL version in the Full chapter gets dropped from OWL-1.1.

The first section of the OWL-Full spec

5.1. The OWL and RDF universes
------------------------------
All of the OWL vocabulary is defined on the 'OWL universe', 
which is a division of part of the RDF universe into three parts, 
namely OWL individuals, classes, and properties. 
The class extension of owl:Thing comprises the individuals 
of the OWL universe. The class extension of owl:Class 
comprises the classes of the OWL universe. 
Review comment from m_schnei 09:57, 21 March 2008 (EDT)
This part of the paragraph doesn't mention datatypes, which are also classes.
The union of the class extensions of 
owl:ObjectProperty, owl:DatatypeProperty, owl:AnnotationProperty, 
and owl:OntologyProperty comprises the properties of the OWL universe.
Review comment from m_schnei 09:28, 21 March 2008 (EDT)
If DL gets dropped, then class owl:ObjectProperty contains every property. Talking about the "union" of the different property types isn't then necessary anymore.
There are two different styles of using OWL.
Review comment from m_schnei 09:45, 21 March 2008 (EDT)
If DL gets dropped, then there will only be one style left.
In the more free-wheeling style, called OWL Full, 
the three parts of the OWL universe are identified 
with their RDF counterparts, namely the class extensions 
of rdfs:Resource, rdfs:Class, and rdf:Property. 
In OWL Full, as in RDF, elements of the OWL universe 
can be both an individual and a class, 
or, in fact, even an individual, a class, and a property. 
Review comment from m_schnei 09:45, 21 March 2008 (EDT)
Complicated formulation. Just say: "In OWL Full, as in RDF, elements of the OWL universe can be an individual, a class, and a property."
In the more restrictive style, called OWL DL here, 
the three parts are different from their RDF counterparts 
and, moreover, pairwise disjoint. 
The more-restrictive OWL DL style gives up some expressive power 
in return for decidability of entailment.
Review comment from m_schnei 09:45, 21 March 2008 (EDT)
If DL gets dropped, then this part of the paragraph will be dropped.
Both styles of OWL provide entailments that are missing 
in a naive translation of the DAML+OIL model-theoretic semantics 
into the RDF semantics.
Review comment from m_schnei 09:45, 21 March 2008 (EDT)
This part of the paragraph seems irrelevant for 1.1-Full.
A major difference in practice between the two styles 
lies in the care that is required to ensure that URI references 
are actually in the appropriate part of the OWL universe. 
In OWL Full, no care is needed. In OWL DL, localizing information 
must be provided for many of the URI references used. 
These localizing assumptions are all trivially true in OWL Full, 
and can also be ignored when one uses the OWL abstract syntax, 
which corresponds closely to OWL DL. But when writing OWL DL in triples, 
however, close attention must be paid to which elements 
of the vocabulary belong to which part of the OWL universe.
Review comment from m_schnei 09:57, 21 March 2008 (EDT)
This paragraph talks about "localization" of URI references. If DL gets dropped, then this paragraph should be changed to an informative paragraph which only talks about the situation in OWL-Full, where (generally) no localization information is needed. It might make sense to compare the situation with 1.1-DL instead of the DL version in the 1.0-Full chapter.
Throughout this section the OWL vocabulary will be 
the disallowed vocabulary from OWL plus the built-in classes, 
the built-in annotation properties, and the built-in ontology properties.
Review comment from m_schnei 09:57, 21 March 2008 (EDT)
This is not a very useful way to "list" the OWL vocabulary. In particular, there is currently no "dissallowed vocabulary" in OWL-1.1-DL. Some other way to present the OWL vocabulary should be considered.