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Re: Review of Semantics Documnt

From: Jeff Z. Pan <pan@cs.man.ac.uk>
Date: Mon, 27 Jan 2003 16:45:49 -0000
Message-ID: <014901c2c623$9e3abdc0$6bc65882@cs.man.ac.uk>
To: <pfps@research.bell-labs.com>
Cc: <www-webont-wg@w3.org>

Peter,

[...]
> > **1. Something I don't quite understand:
> >
> > - section 5.2, why does owl:complementOf have only-if, but not iff
> > characterization, while sameClassAs and disjointWith etc have iff
> > characterizations. I become wondering what will happen if we change e.g.
> > sameClassAs to only-if characterization, does the reasoning rely on the
> > newly added triples?
> >
> The OWL vocabulary that corresponds to DL constructors is given a
> different treatment from the OWL vocabulary that corresponds to
> (other) semantic relationships.  The former have only-if semantic
> conditions and comprehension principles and ; the latter have iff
> semantic conditions.  The only-if semantic conditions for the former
> are needed to prevent semantic paradoxes and other problems with the
> semantics.  The comprehension principles for the former and the iff
> semantic conditions for the latter are needed so that useful
> entailments are valid.
>
> I've added the above wording to the document.

It is much clearer now.

> >
> > **2. some typos:
> >
> > - section 5.2, I(E) should be S_I(E), or atleast introduce/define I(E)
> > somehow like that in RDF MT.
>
> Changed to S_I.
>
> > - section 5.2, "RDFS domains and ranges" part, column 3 of row 1 in the
> > table, "CEXT" should be "EXT".
>
> Fixed.
>
> > - section 5.2, "R_I contains elements corresponding to all possible OWL
> > descriptions and data ranges" part, in the sentence "The first three
> > conditions ... ", why "three", aren't there two? (It should be three if
we
> > consider the third item of part **3.)
>
> There used to be three.  Because of a change, the third one was
> removed.  I've fixed the wording.
>
> > - Appendix B.1, first example line 4, is "value" missed in front of
> > "(ex:author ..."?
>
> Correct, and also missing before ex:name.  This was a recent change
> to the abstract syntax.  There are other places in the document that
> needed a similar fix.
>
> > - Appendix B.1, second example line 2, is "intersectionOf" missed?
>
> No.  There is an implicit intersectionOf here.
>
>
> > **3. minor bugs:
> >
> > - section 5.2, "Some OWL properties have only-if characterizations", the
> > last rule of the second table, "if E is owl:oneOf ...", this is not
common
> > portion of the semantics of OWL/DL and OWL/FULL, thus should be moved to
> > section 5.4. Also in this rule, it seems that "RI OR LV" should be "RI"
or
> > "IOT" (in OWL/FULL they are the same), since LV is already a subset of
RI.
>
> This condition was placed in the common section so that OWL/DL and
> OWL/Full would be very small changes.  It does add more to OWL/DL
> than might be expected.  The change from R_I to IOT is needed,
> however, to make all this work.
>
> Because of the recent changes to the RDF model theory, a better
> version of this can be formulated - one that does not add extra
> oneOfs to OWL/DL while still working for OWL/Full.  I have made this
> change.

It is ok now.


> > - section 5.2, "Some OWL properties have only-if characterizations",the
> > fourth table, "y\in IOC" should be "y\in IOC OR IDC".
>
> Correct. Changed.
>
> > - section 5.2, "R_I contains elements corresponding to all possible OWL
> > descriptions and data ranges", if there exists l, a sequence of x1,...xn
> > over IOT OR LV, then there exist y with y\in CEXT(I(rdfs:Class)),
<y.l>\in
> > EXT(I(owl:oneof)): I think this rule should be moved to section 5.4, and
> in
> > here (section 5.2) should be replaced by two, one for IOT and the other
> for
> > LV, otherwise if x1,...,xn are mixed objects/values, it will cause
trouble
> > to OWL/DL.
>
> I believe that there is no problem here. These elements of
> rdfs:Class would not cause a problem, as they cannot particate in
> most OWL/DL constructs.  However, the recent changes to the RDF
> model theory make a better version possible.

I notice that you did replace the original rule with two, one for IOT and
the other for LV (so I was right).  Now I understand why we don't have to
move it to section 5.4 - the condition "IOT=R_I" for OWL automatically
extend these rules.

Therefore it might be a good idea to mention in section 5.4 and/or 5.2 that
although section 5.2 gives a common portion of semantics of OWL/DL and
OWL/FULL, this common portion has slightly different meaning in OWL/DL and
OWL/FULL due to the three conditions for OWL/FULL.


> > - Appendix B.2, the three antecedent triples don't entail Susan is an
> > object, and friend is an individual property.
>
> You and I misread this section of the document.  I've made it
> clearer.

Yes, I am afraid we did. It is clearer now.


> > **4. Some suggestions:
> >
> > - section 5.2 "Relationships between OWL classes", it is kind of weird
to
> > have  two (or more than two) tables as conditions without any
> explanations.
> > Instead, it might be better if we explain that the relationships between
> OWL
> > classes may be divided into subset relationships (the first table) and
> > membership relationships (the second table).
>
> This has all been reorganized.

I notice that you moved the table about rdfs:domain and rdfs:range to the
first position. It is a good move, so that additional conditions on RDFS are
firstly introduced, then other conditions on OWL. However, since IOP, IOC
and IDC aren't clearly defined so far, shouldn't we add "The meaning of IOP,
IOC and IDC can be found in the following table." behind the first table?


> > - section 5.2 "Characteristics of members of OWL classes": it might be a
> > good idea to have some descriptions before the table. In general, some
> more
> > texts are needed to make section 5.2 easier to understand.
>
> I've reorganized the tables and changed the text.
>
> > - section 5.3, second paragraph, "V'" includes VRDFS, while in section
> > 5.3.2, the last sentence of second paragraph, "V'" is disjoint from
VRDFS.
> > It might be a good idea to change the first one to "V".
>
> Done.
>
> Thanks for your useful review.

You are welcome :)

Jeff

>
> Peter F. Patel-Schneider
> Bell Labs Research
> Lucent Technologies
>
>
>
>
Received on Monday, 27 January 2003 11:44:45 GMT

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