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Re: Review of the RDF based semantics document (CLOSE ACTION-316)

From: Ivan Herman <ivan@w3.org>
Date: Fri, 03 Apr 2009 09:14:22 +0200
Message-ID: <49D5B74E.90101@w3.org>
To: Michael Schneider <schneid@fzi.de>
CC: W3C OWL Working Group <public-owl-wg@w3.org>
Hi Michael,

any response I do not comment on is simply acknowledged as fine!

Michael Schneider wrote:
>> ----------
>> Section 4.1, paragraph staring with "In this document, it will always be
>> assumed from now"
>> The second paragraph seems to be superfluous, it repeats the same
>> message...
> QUESTION: Which "second paragraph" do you refer here? I do not find any redundancy in the text.

Sorry. Re-reading the paragraph it looks o.k. now. Forget it:-)

>> -----------
>> Section 4.2, second paragraph (definition of I),
>> "provided that d is a datatype of D, I(u) = d, and" ->
>> "provided that d is a datatype of D, IS(u) = d, and"
>> Actually... I think a usual abuse of the syntax is to use the I(E)
>> formulation for an interpretation when this means, mathematically, is
>> IS(E) where 'IS' is the mapping defined in 'I'. As this shorthand is
>> used all over the place, it might be worth noting it here.
> I have deliberately chosen to use "I" instead of "IS", since 
> * the RDF Semantics explicitly defines it this way in the "semantic conditions for ground graphs" (Section 1.4 of the RDF Semantics), and
> * the RDF Semantics does use "I" instead of "IS" consistently in the whole document (see for example the table on "RDFS semantic conditions" in Section 4.1 of the RDF Semantics).
> I don't want to deviate from the practice used in the RDF Semantics document without any good reason. One good reason would be that some nomenclature is used throughout the OWL 2 spec in a different form than in the RDF Semantics, but this is not the case here.
> So I am not intending to change this.

I do not ask you to deviate from the RDF Semantics. However, the table
in 1.4 of the RDF semantics _explicitly_ defines, say, I(E) as being
equal to IS(E), ie, introduces a function notation for what is, in fact,
not a function but a tuple. And that is perfectly consistent within the
RDF Semantics text.

Now you are right that this document explicitly refers to the RDF
Semantics, so your usage of I(u) instead of IS(u) is mathematically
correct. But this forces the reader to go back to the RDF semantics text
to understand this, in spite of the fact that this section stands by itself.

I think what has to be done is actually very simple: to add somewhere
some text which says: "following the practice, as also introduced in
section 1.4 of the RDF semantics, the notation I(x) will also be used to
denote IS(x)" or something like that.

>> -------------
>> Comments on Appendix 7 itself
>> Stylistic issues:
>> it may make the proof easier to read if some notations are defined
>> upfront; that would avoid repeating them in the statements and the
>> proofs. I am thinking of:
>>  - G is an OWL DL ontology in Graph form and F(G) is its FS
>> representation, meeting the restriction for DL and that results on the
>> reverse mapping
>>  - D is a datype for OWL FUll, and F(D) its Direct Semantic version.
>> Actually, as an abuse of notation I do not think it would lead to any
>> misunderstandings if F(D) was dropped in the sense that it should be
>> made it clear in the introduction that the there is such thing as F(D)
>> (as defined now) but then say that in the remaining of the section we
>> use the same symbold with the understanding that Direct Semantics is
>> meant in conjunction with F(D)
>> These terms are repeated all over the place (which is, of course,
>> mathematically correct) but makes the reading of the text fairly
>> difficult.
> Thanks! I will think further about this but I am not doing any work on this /now/.
> At least the editorial quality of the proof is certainly not yet comparable with that of the rest of the document, because my main concern was to just have some *technically* satisfying proof before we go to LC. As you can see from the first EdNote at the beginning of the document, I am explicitly planning to further refine the proof, mainly in the time between the start of CR and until PR. I am keeping your comment at a save place till then. :)

I understand, and that is fine. I am happy to re-review the text when
you give me a 'go!'





Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
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Received on Friday, 3 April 2009 07:14:53 UTC

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