LC Responses/JR6b

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See also FH2

As I think another reviewer said, I'm struck by the inconsistent use of "OWL 2", which appears not to refer to anything in particular. I think this is confusing. The structural specification, direct semantics, and RDF mapping, and XML serialization only apply to the DL subset of the language (structural specification), and the document titles and text should reflect this. If you really want to exclude what's now called OWL 2 Full from qualifying as bona fide OWL 2, then please be very clear about this, either by changing terminology or by stating up front the exact relation between OWL 2 Full and OWL 2.

For example: this document says

  This document provides the RDF-compatible model-theoretic semantics
  for OWL 2, called "OWL 2 Full".

while the abstract of SSFSS says

  The ... structural specification ... provides a normative abstract
  model for all (normative and nonnormative) syntaxes of OWL 2.

It's hard to make sense of this. The RDF-based semantics gives a semantics of RDF graphs, only a subset of which correspond to OWL 2 (DL), so of OWL 2 = OWL 2 DL this would only make sense with the qualifier "among other things" and with reference to the SS-to-RDF mapping.


PeterPatelSchneider 20:00, 11 March 2009 (UTC)

[Draft Response for LC Comment 52b:] JR6b

Dear Jonathan: Thank you for your message <http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0068.html> on the OWL 2 Web Ontology Language last call drafts.

Some of your comments in the message relate to specific editorial concerns with the RDF-Based Semantics document. These comments are being addressed in another reply. This response addresses only your comments about the use of "OWL 2", "OWL 2 DL", and "OWL 2 Full".

The working group realizes that our documents did not do a good job of describing the terminology related to OWL 2. To alleviate this problem there is now a new document, the Document Overview http://www.w3.org/2007/OWL/wiki/Document_Overview/.

The structure of OWL 2 ontologies is defined in the OWL 2 Structural Specification and is not limited to ontologies that fit into a Description Logic framework, but you are right in pointing out that this was not made sufficiently clear. The document has been revised so that these features are described in their most general form using examples in both structural and RDF graph forms. Restrictions required in OWL 2 DL ontologies are listed in Section 3, and it is made clear that these only apply to OWL 2 DL ontologies.

The direct semantics directly provides one meaning for the constructs in OWL 2 ontologies. The RDF-based semantics directly provides a meaning for all RDF graphs. As all OWL 2 ontologies can be mapped into RDF graphs, the RDF-based semantics provides another semantics for all the constructs in OWL 2 ontologies.

The phrase "OWL 2", by itself, is now uniformly used to refer to the entire language, regardless of the particular syntax or semantics. The phrase "OWL 2 Full", by itself, is now uniformly used as a shorthand to refer to the treatment of RDF graphs (particularly those RDF graphs that use OWL 2 constructs) under the RDF-based semantics and thus, as you say, is a combination of both syntax and semantics. This use of "OWL 2 Full" is consistent with the use of "OWL Full" in the WebOnt documents that define the original version of OWL.

"OWL 2 DL ontologies" are then those OWL 2 ontologies that admit reasoning using well-known DL techniques when interpreted using the Direct Semantics, and that can be mapped to RDF graphs and back again without affecting their meaning in the direct semantics. This use of "OWL 2 DL ontologies" is consistent with the use of "OWL DL" in the WebOnt documents that define the original version of OWL. Section 3 of the OWL 2 Structural Specification provides a comprehensive and compact list of the extra conditions that are required for an OWL 2 ontology to be an OWL 2 DL ontology.

Several other documents have been edited to better describe how OWL works.The relevant edits have ended up being interspersed with other work, so no diff are provided here. The current working drafts of all the WG documents are linked to from the WG home page.

Please acknowledge receipt of this email to <mailto:public-owl-comments@w3.org> (replying to this email should suffice). In your acknowledgment please let us know whether or not you are satisfied with the working group's response to your comment.

Regards, Peter F. Patel-Schneider on behalf of the W3C OWL Working Group