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Thomas B. Passin wrote:
>
> In my mind, rdf:about='' does not exactly indicate a retrievable resource,
Right, there is no need that rdf:about indicate a retrievable resource.
> although of course at one time it may or may not have been retrieved
(maybe
> not, if the whole thing was created or modified inside an application).
But
> to help me understand this particular point better, please answer this
> question for me -
>
> Is it allowed in OWL - or at least does to make sense to you - to
reference
> some other resource besides the current document in the owl:ontology
> rdf:about attribute? Example -
>
> <owl:Ontology rdf:about='http://example.com/ontology1'>
> <owl:versionInfo>v 1.17 2003/02/26 12:56:51 mdean</owl:versionInfo>
> ....
> </owl:Ontology>
<owl:Ontology> creates a node of rdf:type owl:Ontology, the above parses
into:
<http://example.com/ontology1> rdf:type owl:Ontology .
<http://example.com/ontology1> owl:versionInfo "v 1.17 2003/02/26 12:56:51
mdean" .
This is intended to allow ontologies themselves to be the subject of OWL
inferences.
It would be weird (at least to me) if the URI identified as an owl:Ontology
were not itself dereferencable as an owl:Ontology ... but OWL doesn't
prevent you from shooting yourself in the foot in such a fashion -- it is
assumed that authoring and editing tools will ensure that unsuspecting folks
will do the right thing.
>
> Aside from this special case, and I suppose there are a few others lurking
> around, do you see other situations where it would be important to use an
> actual retrievable URI as an RDF node identifier?
>
Well actually that is the subject of TimBL's proposal to the TAG regarding
the "meaning of rdf:Property URIs". One very reasonable way to define this
would be to dereference the property URI and use what is returned to find a
definition for the property. Suppose the property URI -minus- fragid
identifies a namespace. The namespace document might contain human readable
definitions of the properties defined 'within' the namespace. An OWL
ontology obtained from the namespace might similarly define the properties.
The reason that I use namespace here is that an RDF property is usually
written as a QName although it represents in RDF a URI reference obtained
from concatenating the namespace name with the fragid/local name. e.g.
<rdf:Property rdf:about="http://example.com/foo#bar"; />
is equivalent to the N3:
foo:bar rdf:type rdf:Property .
where "foo" is bound to http://example.com#
Jonathan
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