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RE: Review of Direct Semantics (ACTION 314)

From: Michael Schneider <schneid@fzi.de>
Date: Tue, 7 Apr 2009 23:56:02 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A0011DA96D@judith.fzi.de>
To: "Boris Motik" <boris.motik@comlab.ox.ac.uk>
Cc: "W3C OWL Working Group" <public-owl-wg@w3.org>
Hi Boris!

Unmentioned answers are accepted. Some of the mentioned answers are also (sometimes weakly) accepted, if this is explicitly stated.

Boris Motik wrote on April 06, 2009:

>Hello Michael,
>
>Thanks a lot for your review. Please find my answers inline.
>
>Regards,
>
>	Boris

>> * General: The definitions in the document, in particular those in
>§2.5, are
>> of the form "A if B". While this is a typical convention under
>mathematicians,
>> our documents are targeted to a broader audience. In order to avoid
>confusion,
>> I suggest to always say "if and only if" (or "iff", and say once that
>this
>> means "if and only if").
>
>I've had extensive discussions about this with many people (notably
>Uli), and they insisted that the latter form is rather ugly. I'd prefer
>leaving things as they are.

I cannot really be ok with this answer, since this is not a matter of ugliness, but a matter of correctness. I had a related review comment for the RDF-Based Semantics, but there, it was only about replacing the term "iff" by "if and only if" for clarity. Just for the record: In the RDF-Based Semantics, I won't agree to change the definitions there to "if", if "if and only if" is actually meant. However, given that an "if" in definitions is a widespread convention, I won't further request any changes, unless someone else in the WG concurs.

Weakly (and conditionally) accepted.

>> * §1, 2nd par: "Since OWL 2 is an extension of OWL DL, ..." Didn't we
>want to
>> turn away from this statement?
>>
>
>But this actually is true: each OWL DL ontology is an OWL 2 DL ontology,
>and it is therefore an OWL 2 ontology. Hence, I don't really see a
>problem with this statement.

Yes, you are right. But what I actually had in mind was that we 
had LC comments on this particular kind of statements, 
for example LC 28/FH2, which specifically refers to this phrase in the 
Direct Semantics:

  <http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0035.html>

So, I strongly suggest to change the text here.

I can see that, in this particular case, this statement is a rational
for the observation that the Direct Semantics is also a semantics for
the original OWL DL and OWL Lite. So, that's really good information 
that people will be happy to learn.
 
Suggestion, why not start the sentence with something approximately like:

  "Since this semantics in this document is an extension 
  of the Direct Semantics of OWL 1 ..."

IMHO, this will be completely uncontentious for people outside the WG, 
and will still meet the purpose of the sentence.

>> * §2.1, before the list concerning datatype maps: The sentence ends
>with "with
>> the following components.", i.e. with a ".". In other places, e.g. the
>> following list for "vocabularies", there is a ":" instead. Consider
>being
>> coherent.
>>
>
>I've changed "." into ":".

Found still one "." in §2.2. :-)

>> * §2.1, list of items (and other places): I always wondered why the
>pairs,
>> such as "< F v >" and "< LV DT >" do not contain a comma, while other
>pairs
>> later in the document do have a comma? Consider being coherent.
>>
>
>Fair enough -- I've added a comma everywhere. I've also updated the
>notation in the Syntax document.

Ok. But I found that you missed Syntax §7.5 (DatatypeRestrictions).

>> * §2.1, datatype maps, last item: I find the name "facet value"
>somewhat
>> confusing, since (a) it is actually a set and (b) I rather would
>expect the
>> "v" in a pair "< F v >" to be called the "facet value". I wonder if
>there is a
>> better name for this, but have to admit that I do not really have an
>> alternative. If this is going to change, than other documents might
>need to be
>> changed, either.
>>
>
>Fair enough. I've actually avoided giving this thing a name and have
>just said that the interpretation function assigns to < F v > a set (< F
>v >)^FS. I've also changed the Syntax document accordingly. (There, only
>the heading of Table 4 needed to change.)

For the record: I also have not given any concrete name for this set
in the RDF-Based Semantics. So there is alignment.

Accepted!

>> * §2.1, vocabularies, 4th item: Are you sure that V_I contains
>anonymous
>> individuals, which are existential variables?
>>
>
>Yes. This is not a problem, however: we require the anonymous
>individuals in Ax to be standardized apart and we have appropriate
>restrictions in the definition of models. Introducing yet another
>syntactic construct would just complicate matters.

I understand the idea of "standardizing apart" bNodes, it's the same in RDF.
But I wondered why bNodes can actually be part of an interpretation's vocabulary.
Formally, they are variables bound to some existential quantifier that surrounds
the "logic expression" that is given by a concrete ontology.

But I'm ok with this answer. I just wanted to check whether this was just
an oversight.

Weakly accepted.

>> * §2.2.2: "An n-ary data range DR is interpreted as an n-ary relation
>(DR)^DT
>> over Δ_D." Please be more explicit what this means, just as you are
>more
>> explicit earlier in this paragraph on what "unary relation over
>DELTA_D"
>> means, namely "(DT)^DT subset DELTA_D". You probably mean "(DR)^DT
>subset
>> (DELTA_D)^n"?
>>
>
>Thomas had a comment about this, and I've rephrased the paragraph in
>response to him. Please let me know should you find the new formulation
>insufficient.

I can see that the text has changed. However, the change did not
touch the part of the text to which my comment referred. So my 
comment is still open.

What I meant is to have for n-aries a text analog to the phrase:

  "— that is, as a set (DT)DT ⊆ ΔD"

Cheers,
Michael

--
Dipl.-Inform. Michael Schneider
Research Scientist, Dept. Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: michael.schneider@fzi.de
WWW  : http://www.fzi.de/michael.schneider
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Received on Tuesday, 7 April 2009 21:56:45 GMT

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