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Lyndon J B Nixon wrote:
> skimming through the OWL spec, and trying to grasp it -- as it is an
> extension of RDF Schema just like DAML+OIL
> it can express constraints upon RDF assertions, but what about XML (not
> RDF) vocabularies?
This generally was a feature called "structured XML datatypes" that didn't
make it (as it currently looks) into the first version of OWL, and will
likely be postponed for a later version of the languages.
I have been the main agitator for including this in OWL, but there are
several (little) problems at present which prevent such features from
actually being tested, implemented etc.
There is a partial solution, for simple datatypes, that I'll discuss below.
It is possible that a general solution can be _built on_ OWL as it stands
today, but someone needs to do that.
>
> i.e. considering TBLs layers for the Web
>
> Ontologies e.g. OWL
> Metadata e.g. RDF
> Data e.g. XML
>
> Can the ontological layer only be built upon the metadata layer? if so,
> how could I state equivalences and other
> relationships between XML elements/attributes? Isn't that just as
> necessary? Or is this why we're being suggested
> to write XML which can map well into RDF? ;)
One of the problems is that XML Schema names its types using QNAMES and
there isn't a straightforward general transform into URIrefs which are used
by RDF/OWL to name its classes. This remains a TAG issue and the XML Schema
WG is working on it, but since it is not yet solved, OWL can't use any such
future solution to test any implementations/interoperability today. Since we
can't test it the feature has been postponed for a later time.
>
> lyndon
>
> NB One sentence summary: I can assert myrdf:ZipCode owl:samePropertyAs
> yourrdf:PostCode
> but why can't I also assert myxml:ZipCode owl:sameDatatypeAs
> yourxml:PostCode.
>
How about this:
<owl:DatatypeProperty rdf:ID="ZipCode">
<rdfs:range rdf:resource="&myxml;ZipCode"/>
</owl:DatatypeProperty>
<owl:DatatypeProperty rdf:ID="PostCode">
<rdfs:range rdf:resource="&yourxml;PostCode"/>
<owl:samePropertyAs rdf:resource="#ZipCode" />
</owl:DatatypeProperty>
Now you might imagine why doing this with XML datatypes would get tricky --
you'd need some XML datatype aware software that can compare "PSVI"s for
equality etc. Its alot easier to write simple datatype aware software that
understands equality for numbers, dates etc.
Jonathan
http://www.jonathanborden-md.com
http://www.erieneurosurgery.com
http://www.openhealth.org
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