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Re: bNodes wanted

From: Sandro Hawke <sandro@w3.org>
Date: Sat, 25 May 2002 07:25:22 -0400
Message-Id: <200205251125.g4PBPMB19740@wadimousa.hawke.org>
To: Dan Brickley <danbri@w3.org>
cc: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, www-rdf-interest@w3.org

danbri writes:
> On Fri, 24 May 2002, Peter F. Patel-Schneider wrote:
> > Sandro writes:
> > > It seems like the question is whether I can properly generate a Skolem
> > > constant.  There are several ways to generate URIs that no one else
> > > will ever generate; you can pick one that meets your needs:
> > >
> > >     - the tag: URI algorithm for human-readable ones [1]
> > >     - the UUID algorithm for easy machine generation
> > >     - a cryptographicaly secure random number if you're
> > >       seriously concerned about duplicate generation
> > >       (such as by malicious 3rd parties)
> >
> > None of these work.  As soon as any other agent sees the skolem URIrefs
> > then it can use the URIrefs, resulting in them possibly being used in other
> > doucuments.

[ Which is exactly what I said, of course, only I didn't characterize
it as "not working". ]

> 
> Hey we agree on something :) Absolutely right.
> 
> 
> > > If you also want to make sure no one can use it after the fact, then
> > > you certainly need bNodes.  But I don't know why you'd want that.  Use
> > > cases?
> >
> > Lets see:
> >
> > 1/ containers that cannot be added to by other parties
> > 2/ resources that cannot be referred to by name, only in terms of their
> > relationships to other resources
> 
> I guess for 1/, you'd need to be careful not to describe your container
> with enough information (such as a daml:UnambiguousProperty, in the
> simplest case) to allow others to easily say things about it afterwards.
> I'm not sure that's always achievable. You might have some container and
> not want anyone to talk about it afterwards; yet others might start
> describing it (in RDF+WebOnt/etc) as 'the rdf:Seq that Peter mentioned in
> his message of 2002-05-25'. I don't think this can be avoided. Instead,
> we'd want strategies to avoid believing things claimed in such a matter,
> perhaps?

Right.  Once you've said something in a message, it's hard to stop
people from jumping in with their related information.  Using bNodes
makes it harder (perhaps impossible in some graphs with no
disambiguating properties), but RDF came from the Metadata Initiative
and I think allowing people to connect their own information was (and
remains) an important design goal.  I think bNodes are mostly in the
language as a convenience for human authors (who don't want to have to
name everything).

And of course, as danbri says, we need ways to manage trust in such
additional information.

   -- sandro
Received on Saturday, 25 May 2002 07:26:07 GMT

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