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Re: Review of Semantics Documnt

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 02 Jan 2003 13:13:37 -0500 (EST)
Message-Id: <20030102.131337.133256067.pfps@research.bell-labs.com>
To: hendler@cs.umd.edu
Cc: www-webont-wg@w3.org

From: Jim Hendler <hendler@cs.umd.edu>
Subject: Review of Semantics Documnt
Date: Wed, 1 Jan 2003 17:36:58 -0500

> Review of 
> http://www-db.research.bell-labs.com/user/pfps/owl/semantics/  31 
> Dec, 2002.

[...]

> Summary:with the exception of the one meta-comment below, I thin the 
> document is in good shape and I have only minor typographical comments
> 
> 
> meta-comment: the document is not consistent in its treatment of OWL 
> DL v. OWL Full - this is okay since it is mostly about DL, but makes 
> some of the text uneven because sometimes it says things like "cannot 
> be translated into an OWL/DL graph" to mean that something is in 
> Full, but not DL, but othertimes it says things like "OWL Property 
> Axioms " to mean specifically the OWL DL ones (i.e. maintaining the 
> separation of data and object types).  The editor should go through 
> the document and try to be more consistent, and probably should add a 
> comment near the top saying something like "unless otherwise 
> indicated, in this document "OWL" will be used to denote the DL 
> subset of OWL" and explaining why-- this might be done simply by 
> promoting the paragraph
> 
> >The abstract syntax here is less general than the exchange syntax 
> >for OWL. In particular, it does not permit the construction of 
> >self-referential syntactic constructs. It is also intended for use 
> >in cases where classes, properties, and individuals form disjoint 
> >collections. These are roughly the restrictions required to make 
> >reasoning in OWL be decidable, and thus this abstract syntax should 
> >be thought of a syntax for OWL/DL.
> 
> to section 1.2 and giving it a heading, so as to emphasize it (and 
> make it so people who skip to a middle section from the index cannot 
> as easily miss this comment)

I've made a number of stylistic changes in an attempt to alleviate this
problem.  I haven't, however, moved the above paragraph up to the
introduction.  I would prefer not to do this, but may end up doing it
nonetheless, if I can't figure out a better way.

> 1) section 1.1  Differences from DAML+OIL reads:
> 
> >The only substantive changes between OWL and DAML+OIL are
> >
> >     * the removal of qualified number restrictions, per a decision of WebOnt;
> >     * the ability to directly state that properties can be 
> >symmetric, per a decision of WebOnt; and
> >     * the absence in the abstract syntax of some abnormal DAML+OIL 
> >constructs, particularly restrictions with extra components.
> 
> but of course that is no longer true.  

Hmm.  I don't think so.

> This is true of OWL DL, not of 
> "OWL" - and this section should probably also list the changes for 
> OWL Full (i.e. eases separation restrictions) - the introdcution 
> doesn't mention Full v. DL at all and it should (which is easily done 
> by just mentioning it and providing a forward pointer to section 5.4 
> and/or A.2 as necessary.

DAML+OIL didn't have the separation.  I've added some wording that
hopefully makes things clearer.


> 2) section 3 - Direct M-T semantics - (tiny style point) first 
> sentence is hard to parse (esp. with misplaced "Section 5" words) 
> maybe make it
> 
> This model-theoretic semantics for OWL goes directly from ontologies 
> in the abstract syntax to a standard model theory. Thus is simpler 
> than the semantics for RDF graphs, described in Section 5, which is 
> based on a vocabulary extension of the RDFS model theory (Add 
> citation link).

I've made a change very close to this.

> 3) The following sentences from section 3 is technically fine, but 
> some what odd
> 
> >The semantics here starts with the notion of a vocabulary, which can 
> >be thought of as the URI references that are of interest in an OWL 
> >ontology. It is, however, not necessary that a vocabulary consist 
> >only of the URI references in an OWL ontology.
> 
> maybe reqord to make clearer (I'm okay leaving as is, but it might be improved)

I'm not sure how to make this clearer.

> 4) near end of section 3 it says:
> 
> >An Abstract OWL ontology entails an OWL axiom or fact if each 
> >interpretation of the ontology is also an interpretation of the 
> >axiom or fact. An Abstract OWL ontology entails another Abstract OWL 
> >ontology if each interpretation of the first ontology is also an 
> >interpretation of the second ontology
> 
> are these "if" or should they be "if and only if" (in particular for 
> the second one)

Hmm.  The convention is to say if here, because it is defining entailment,
but to mean iff.  I'm rather unwilling to make a change.

> 5) Section 5.1, second paragraph says
> 
> >In the more free-wheeling style, called OWL/Full here,
> 
> delete the word "here"

Done.

> 6) Section A.2 claims to be a "Poof Sketch" - an amusing typo but it 
> probably should be fixed.

Done.

> 7) I'm not opposed to Appendix B, but in my mind it isn't of much 
> use, could be deleted

Hmm. I would be willing to delete it as well, but I seem to remember some
comments to the effect that examples were needed.

peter
Received on Thursday, 2 January 2003 13:13:48 GMT

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