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retrievable URIs in RDF, was Re: more politics

• To: "Thomas B. Passin" <tpassin@c...>, <xml-dev@l...>
• Subject: retrievable URIs in RDF, was Re: more politics
• From: "Jonathan Borden" <jonathan@o...>
• Date: Fri, 25 Jul 2003 09:56:14 -0400
• References: <r02000000-1026-BC099F40BD6811D7A0870003937A08C2@[192.168.124.11]> <oprssgstsbezizxn@s...> <009e01c35183$41d1f3f0$6401a8c0@tbp1> <20030724013426.GE22456@m...> <00b201c35191$53370b90$6401a8c0@tbp1> <09d801c35240$c4b55ab0$b6f5d3ce@s...> <012801c3525c$28de9310$6401a8c0@tbp1>

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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