W3C home > Mailing lists > Public > www-rdf-interest@w3.org > May 2000

RE: Anonymous resource names -versus- variables

From: McBride, Brian <bwm@hplb.hpl.hp.com>
Date: Wed, 3 May 2000 21:49:45 +0100
Message-ID: <7686E88F1253D311A867006008CD059F010B1D99@0-mail-1.hpl.hp.com>
To: www-rdf-interest@w3.org
>I've been thinking about this a fair bit lately. Contrary to 
>(my reading
>of) Sergey's perspective on this, I don't believe we should 
>generate URIs
>for anonymously mentioned resources since they may well 
>already have 'proper'
>URIs that we're unaware of. So instead of assigning a URI, i believe we
>need some way of tracking the fact that we don't really know 
>the name of
>the resource.

I'd agree that this approach better implements the m&s spec.


>Specifically, I'm thinking of something like an implementors 
>convention to
>use a certain subset of URIs when naming resources whose 
>"proper" URI we
>don't know. 

As a point of principle, is it a good idea to adopt implementors
conventions which may constrain the future development of other
specifications?  I would suggest first exploring whether
the issue can be solved within the context of RDF implementation.

So far as I'm aware, there is no concensus on an 'implementation model'
for RDF tools and components.  Such a model would be a good thing, 
but lets just consider a part of it right now.

What is the output interface for an RDF parser?

Lets propose that there might be two:

	o an API to an RDF store or other program (which is what SiRPAC
currently does)
	o a serialized stream of triples

The current Stanford RDF API handles anonymous resources very nicely.

For a serialized stream of triples, it is a trivial problem to design
a stream format which clearly distinguishes between URI's and an
anonymous ID space.  For example,

  [URI:'...', URI:'...', Literal:'...']
  [Anon:'...', URI:'...', Anon:'...']

but you might want to make it an XML format language.

Does this solve the problem?  I suggest there is no motivation here
to invent variable URI's.

>... However when an RDF parser outputs the
>extracted RDF data, some other convention is needed to hook 
>together the
>graph. Where we have public URIs for the resources, they do 
>fine; where we
>don't, we have cludges. The current cludge in many RDF parsers 
>seems to be
>to use a made up URI based on the source of the data with 
>"genid_n" tacked on
>the end.

The current implementation of SiRPAC allocates digest
URI's for anon resources, but I don't believe there is a need for
it to do so given that it uses the Stanford RDF API to produce its
output.  I haven't done a full parser, but I have test code that
drives that API and produces models with anon resources.  What do
you think Sergey?

I'm not saying that 'var:' URI's are a bad thing - I don't have a
view right now.  But is this RDF issue a good motivation to invent

Received on Wednesday, 3 May 2000 16:50:09 UTC

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