- From: Brian McBride <bwm@hplb.hpl.hp.com>
- Date: Mon, 23 Jul 2001 07:40:12 +0100
- To: Graham Klyne <GK@NineByNine.org>
- CC: RDF core WG <w3c-rdfcore-wg@w3.org>
Graham Klyne wrote:
[...]
> 4. Can we agree whether or not unique generated IDs (in the style of Skolem
> constants) are equivalent to existentially quantified variables for the
> purpose of asserting the existence of a resource with properties
> given? (See Frank's message [10] for a discussion -- I discount the option
> of dropping anonymous resources.)
This is the key question. I suggest we have established the following
differences between a resource named by a URI and a resource identified
by a quantified variable:
o scope: An application given a resource identified by a URI
can reasonably expect to pass that URI to other applications and
that they should be able to recognise it - c.f. my example
on seeking references about a service offered in response to an ad.
If the response includes a reference to a service identified by
a URI, the receiver could reasonably pass that URI to reference
service to seek a credit/quality reference for that service.
There is no point doing that for a variable.
o binding: An application given a resource identified by a URI
can assume that URI denotes a specific resource - the
binding decision has been made - an existentially quantified
variable has not been bound to a specific resource.
o provenance: when a source of rdf states some properties about
a resource named by a URI it is making assertions that the
resource named by that URI has those properties. when a source
of rdf states properties about a variable, it is making no
assertions about the name of that resource.
Brian
Received on Monday, 23 July 2001 02:42:49 UTC