Richard
Bijan, Knud, Bernard, thanks for the clarification.
I'm indeed surprised! Subclassing rdfs:label is okay in RDFS, and it
is okay in OWL Full, but it is not allowed in OWL DL.
The issue here is not that subclassing annotation properties is
forbidden by OWL-DL, which is explainable and defendable. The real
mistake of OWL, IMHO, is to have defined rdfs:label as a built-in
annotation property, and not as a datatype property, and with no
built-in alternative for dealing with names (beyond URIs). Defining
rdfs:label as an annotation means that you can't build any OWL-DL
inference whatsoever based on the value of rdfs:label, and that you
can't define various types of "names", to which you would want to attach
specific semantics, as subproperties of rdfs:label. For example
skos:prefLabel and skos:altLabel are not defined as subproperties of
rdfs:label, and if they were SKOS vocabulary would be OWL-Full instead
of OWL-DL. But interfaces such as Tabulator need a value of rdfs:label
for resource display, so in the description of a skos:Concept you have
to repeat the value of skos:prefLabel in a rdfs:label field to make
Tabulator happy. This is suboptimal at least.
The RDF consumers I'm working on (RDF browsers and the Sindice engine)
don't care if you're in OWL DL or not, so I'm tempted to argue that it
doesn't matter much for RDF publishing on the Web. (IME, on the open
Web, trust and provenance are much larger issues than inference, and I
don't believe that the open Web will ever be OWL DL, so why bother.)
Well, the above example shows it's not a minor issue. DL-based inference
does not necessarily mean involving arcane axioms and complex
deductions. Even for Web publishing, interfaces willing to display
"intelligently" the names (such as skos:prefLabel) of a resource need a
minimal level of inference over the various type of names. The fact that
those interfaces rely on rdfs:label for dispaly is indeed an issue. If
OWL had a built-in owl:label datatype property, this would be much
easier to deal with ... Is anything along thoses lines intended in OWL 2.0 ?
Bernard
Others here will probably have different perspectives on this question.
Indeed :-)
Bernard
Richard
On 28 Jul 2008, at 17:01, Bijan Parsia wrote:
On 28 Jul 2008, at 16:23, Richard Cyganiak wrote:
On 28 Jul 2008, at 15:52, John Goodwin wrote:
In an ideal
world, John would declare pub:name a subproperty of
rdfs:label, and the tools would infer the rdfs:label value...
But most clients don't do that yet.
Am I allowed to declare something as subproperty of rdfs:label?
As far as I know, yes.
I'm
guessing this is one of those things that is allow in RDF, but not in
OWL DL?
I would be surprised if that is the case.
You're surprised.
What makes you think so?
The spec? :) But also you can try one of the species validators.
(rdfs:label is an annotation property and you are not allowed to
subproperty annotation properties in OWL DL)
http://www.w3.org/TR/owl-semantics/syntax.html#2.1
"""Properties relate individuals to other information, and are
divided into four disjoint groups, data-valued properties,
individual-valued properties, annotation properties, and ontology
properties"""
Then if you look at the rest of the grammar, you'll see where
annotation properties are allowed.
Can anyone else comment on this?
(FWIW, foaf:name is a subproperty of rdfs:label.)
And hence, not OWL DL.
Historywise, this sort of annotation is a kind of metamodeling. At
the time, the WebOnt working group (at least the DL contingent)
wasn't sure how to handle this (it's not a standard feature of
logics, esp. if you give it a strong semantic reading a la OWL Full).
So the compromise was to forbid this.
In OWL 2 (DL), you can get this sort of effect two ways, annotations
(which are under discussion and being explored) or by punning classes
and individuals (which won't actually help you with the built in
vocabulary).
Typically, subpropertying rdfs:label isn't really a *domain modeling*
thing, but an attempt to spec a *presentational* issue (i.e., many
UIs exploit rdfs:label, and one wants to indicate which properties
should show up in the UI). Thus, there's a bit of tension there.
HTH.
Cheers,
Bijan.
--
*Bernard Vatant
*Knowledge Engineering
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