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RE: Review OWL 2 MT Semantics Document

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Mon, 8 Sep 2008 08:55:36 +0100
To: "'Thomas Schneider'" <schneidt@cs.man.ac.uk>
Cc: <public-owl-wg@w3.org>
Message-ID: <001a01c91188$4756dff0$2b12a8c0@wolf>

Hello,

> -----Original Message-----
> From: Thomas Schneider [mailto:schneidt@cs.man.ac.uk]
> Sent: 07 September 2008 13:42
> To: Boris Motik
> Cc: public-owl-wg@w3.org
> Subject: Re: Review OWL 2 MT Semantics Document
> 
> Hi Boris,
> 
> thanks very much for your response and the changes you've made. I
> agree with most of them, but have comments about the following ones:
> 
> >> * 2.1 Vocabulary
> >>
> >> - Definition of N_{DT}: This is inconsistent with the OWL 2
> >>   Specification: in Section 4
> >>   [ http://www.w3.org/2007/OWL/wiki/Syntax#Datatype_Maps ] , it says
> >>   that N_DT *must not* contain rdfs:Literal.
> >>
> >
> > All sets in the definition of the vocabulary are now called V_*.
> > Thus, we now have N_DT in the datatype map and V_DT in the
> > vocabulary. I hope things are now clearer.
> 
> I think it's a good idea to change the N_* to V_*. However, now the
> vocabulary V *over D* is not related to D any more: the enumeration of
> the V_* should at least contain the statements V_{DT} = N_{DT}, V_{LT}
> = N_{LT}, and V_{FA} = N_{FA}, shouldn't it?
> 

That was already there; for example, the text said V_LT is the set of all literals of D. Nevertheless, I added an explicit equality
to make things clear.

> >> * 2.2 Interpretations
> >>
> >> - Definition of Delta_D: The notion (DT)^{DT} is very
> >>   confusing. Please don't use 'DT' for different things (datatype
> >>   and superscript of the interpretation function). One of these can
> >>   be replaced, e.g., by the lower case symbol 'dt'. The same for
> >>   ''OP'', ''DP'', ... -- and, of course, in the Syntax document.
> >>
> >

[snip]

I appreciate this concern; however, I simply don't see a nice solution to this.

[snip]

> OK, I find it clearer now. However, I now have the same problem as
> Michael: my Firefox 3 shows the "alpha" as an italicised "a", while
> Firefox 2 showed a clear "alpha". How about turning the "alpha" into
> an "x" here?
> 

Agreed -- I've changed it to "x".

[snip]

> Thanks, but I'm not 100% satisfied with the new heading "Keys":
> Strictly speaking, "KeyFor(PE_1, ..., PE_n, CE)" is a key
> *constraint*. A key is an n-tuple of individuals filling the
> properties PE_1, ..., PE_n. Being picky, I'd rather like to see the
> heading "Key Constraints" here ...
> 

I'd prefer avoiding the term "constraint", as it might be confused with "integrity constraints". The difference between integrity
constraints and axioms is something that is confusing OWL users quite a bit in general. Furthermore, I'm not sure why this type of
axioms should be called a constraint while other axioms should not: all of them are just first-order sentences.

> >> [Semantics of key constraints]
> >
> > In private communication Peter has suggested an even shorter way of
> > writing this condition.
> 
> Good, much clearer! I just feel that it should be made clearer that
> the antecedent of the "imply" is everything behind the colon. I know
> that this property doesn't make sense otherwise, but an extra pair of
> brackets or so might help the reader to grasp the structure of this
> non-trivial statement.
> 

I'd prefer not introducing brackets because this statement is meant to be read as a natural-language statement. I appreciate your
concerns, though, so I've reformatted and rephrased the condition a bit to make your point clearer (I hope). 

[snip]

> >> - Proof, third-last sentence ("Clearly, ComplementOf(DT)^DT subset
> >>   ComplementOf(DT)DT'"): The map .^DT' hasn't ben defined because
> >>   Int' uses .^DT. Furthermore, why is it enough to consider only
> >>   data range expressions of the form ComplementOf(DT) and not
> >>   ComplementOf(DR) for arbitrary DR, or DatatypeRestriction(DT,
> >>   ...)?
> >>
> >
> > D' should use .^{DT'}; this was a typo.
> 
> Well, this was my mistake: I overlooked the fact that .^{DT'} was
> given in D'. Now there's Michael's comment that .^{C'} isn't defined.
> 

Oh, yes, sorry!

[snip]

Thanks again, and let me know should you have further comments.

Regards,

	Boris
Received on Monday, 8 September 2008 07:57:15 GMT

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