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Re: "ObjectProperty" and "DatatypeProperty"

From: Kevin D. Keck <kdkeck@lbl.gov>
Date: Fri, 18 Jul 2003 14:09:24 -0700
To: Jim Hendler <hendler@cs.umd.edu>
Cc: public-webont-comments@w3.org
Message-Id: <200307181409.24591.kdkeck@lbl.gov>

Sure, I'll move the naming discussion to the rdf-logic list, but that was only 
the first part of my comment.

The second was that I, at least, was confused about whether (in OWL-DL)
owl:Class'es are owl:Thing's. I thought the idea is that they're not, but then 
I came across the "Class instances are all OWL objects" statement (AS&S, Sec 
5.2, see below). What does this mean? Does this mean owl:Class'es _are_ 
owl:Things? Or does it mean they're both in the range of owl:ObjectProperty 
(contrary to the range given)? And if not, then what subclass of Property 
includes rdf:type? Some class there's no name for?
-- 
Kevin D. Keck
http://vimss.lbl.gov/~kdkeck/
510-486-4856


On Thursday 17 July 2003 16:41, you wrote:
> Kevin-
>   thanks for your comment - the WG spent a long time considering
> different names for these things - but in each case the alternatives
> had some community that would think we meant something different.
> However, the charter by which our WG was set up said:
>
> "If in this process the Working Group finds solutions that are agreed
> to be improvements over solutions suggested by DAML+OIL, those
> improved solutions should be used."
>
> and, unfortunately, in this case nothing was found that was agreed to
> be an improvement over the D+O solutions, and thus in the end we kept
> those names which had been used successfully in a large number of
> ontologies (see http://www.daml.org/ontologies for 240+ examples).
> If you have specific suggestions, or simply want to see if the
> discussion exposes better names, please send email to
> www-rdf-logic@w3.org and if we see a wide consensus that some other
> names are better, we would certainly consider that as evidence that
> we might reopen this issue, but barring that, we will keep the widely
> used DAML+OIL names.
>   Please respond, cc-ing public-webont-comments@w3.org, whether this
> response is satisfactory.
>   -Jim
>
> >While most of the spec. has been tightened up nicely, I'm afraid the names
> > of the two main OWL Property classes are still terribly confusing, and
> > may obscure a significant ambiguity.
> >
> >First off, a natural English speaker's intuition is that something named
> >"ObjectProperty" would be the class of Properties of Objects, i.e., whose
> >_domain_ was (a subset of) Object. This is doubly confusing, because in
> > the RDF spec "object" is defined as the _value_ of a predicate/Property.
> > In fact, this is actually triply confusing, because in RDF "object"
> > refers to the value of _any_ Property, specifically including literal
> > values. As if to admit this problem, the AS&S actually uses
> > "individualvaluedPropertyID" as the name of the corresponding abstract
> > syntax element. This name is much better, but unfortunately it is not
> > clear to me that it is entirely accurate either (see below).
> >
> >Perhaps even more pernicious is the name "DatatypeProperty", which is used
> > to refer not even to Properties whose values are rdfs:Datatype's, but
> > rather to Properties whose values are rdfs:Literal's. The name used in
> > the AS&S ("datavaluedPropertyID") for the corresponding abstract syntax
> > element is only barely tolerable; obviously the much more transparent
> > names would be LiteralValuedProperty and literalValuedPropertyID.
> >
> >Lost in all this is an apparent ambiguity in the spec. Despite having no
> >formal definition of the term "object", section 5.2 of the AS&S
> >(http://www.w3.org/TR/owl-semantics/rdfs.html#5.2) asserts (in the second
> >table, "Characteristics of OWL classes, datatypes, and properties") that
> >"Class instances are all OWL objects."  However, section 5.4
> >(http://www.w3.org/TR/owl-semantics/rdfs.html#5.4) insists that IOT and
> > IOC must be disjoint. Thus, clearly "OWL objects" must refer to the union
> > of IOT and IOC, right? Only, returning to 5.2, interpretations of
> > owl:ObjectProperty asserted to be contained in IOTxIOT. Well, which is
> > it? Are Classes Objects, i.e., is IOC a subset of IOT, or not?
> >
> >And if not, then what type of Property are rdf:type, rdfs:range,
> > rdfs:domain, etc. in the OWL universe?
> >--
> >Kevin D. Keck
> >http://vimss.lbl.gov/~kdkeck/
> >510-486-4856
Received on Friday, 18 July 2003 17:09:35 GMT

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