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Re: Anonymous resource names -versus- variables

From: Guha <guha@epinions-inc.com>
Date: Thu, 04 May 2000 11:00:26 -0700
Message-ID: <3911BABA.737C5574@epinions-inc.com>
To: Dan Brickley <danbri@w3.org>
CC: Sergey Melnik <melnik@db.stanford.edu>, Jan Wielemaker <jan@swi.psy.uva.nl>, Dave Reynolds <der@hplb.hpl.hp.com>, www-rdf-interest@w3.org
Yes, Anonymity is not a property of the object, but a property
of the description of the object. The situation is similar to
indexicals. I can use "he" to refer to Dan, but that does not mean
Dan is of type "he" or "indexical".

guha

Dan Brickley wrote:

> On Thu, 4 May 2000, Sergey Melnik wrote:
>
> > Instead of associating semantics with URIs one could state it
> > explicitly:
> >
> >       book1 --author--> var:....
> >
> > would become
> >
> >       book1        --author-->   whatever_URI
> >       whatever_URI --rdf:type--> rdf:Anonymous
> >
>
> Interesting approach, but I don't think that quite works. We really
> shouldn't be calling these "anonymous resources" as that leads us to
> think that the resource itself is intrinsically nameless. That habit leads
> us to solutions such as yours, which suggest that the anonymity is a
> property of the resource, rather than of some mention or description of
> the resource. Since I don't think anonymity is a property of the resource,
> your proposal expresses exactly what I'm disagreeing with!
>
> I argued a similar point last month:
> http://lists.w3.org/Archives/Public/www-rdf-interest/2000Apr/0022.html
>
> excerpt:
> > Sometimes we don't know the commonly agreed ID for some entity, but
> > nevertheless write some RDF statements that mention it in passing. When
> > we send someone an RDF model and lack such URIs (sometimes because of
> > partial knowledge; sometimes because social process
> > doesn't exist to give uncontroversial URIs to these entitites) we still
> > need to represent those entities in some kind of data structure.
> >
> > So these are the so-called 'anonymous resources'. I really think this is a
> > bad name; it suggests that the anonymity is in some way intrinsic to the
> > resource. That's not the case: rather, some 'mention' of that resource is
> > anonymous in that we happen not to name the resource on that occasion.
>
> I agree with you that associating semantics with special URI schemes for
> use with RDF isn't a great solution, but feel the analogy with variables
> makes this worthy of some investigation.
>
> RDF's world consists solely of Web-nameable resources (things for which
> the notion of identity makes sense, and which may/might/can have URIs) and
> un-nameable (intrinsically anonymous??) literal strings. RDF applications
> that express queries, inference rules etc. typically add to this some
> notion of a variable. eg. TimBL's DesignIssues work
> (eg. http://www.w3.org/DesignIssues/Toolbox.html) makes a stab at doing
> this.
>
> Anyone representing rules/queries over RDF content (and hence
> using variables) needs to decide whether those data structures will
> themselves have a representation in the RDF 1.0 Model, or whether they'll be
> inexpressible in the core model and be represented in a superset of RDF
> 1.0 that has an explicit notion of variables. As Tim says in the Toolbox
> doc. (discussing NOT, rather than variables, but general point holds)...
>
>         'As RDF has little power at its basic level, anything new has to be
>         introduced by reification - by describing it in RDF. Hence, to say
>         "not(node, property, value)", you have to say, for example, "there is
>         something which is an RDF property and has a subject of A and whose B
>         property has vale C and is false". '
>
> So if I want to represent variables within an RDF context, we either
> find a hack that appeals (eg. "var:" IDs) or admit that certain things are
> not elegantly represented in base RDF (although of course they can be
> "tunnelled through" the RDF triples model, ie. quoted
> but not understood by most 1.0 processors).
>
> I've seen quite a few systems tunnel rules (containing variables) over
> RDF, eg. Jos De Roo's work (ftp://windsor.agfa.be/outgoing/RCEI/NET/euler/index.html)
> which lead me to suggest that the anonymous node problem and the
> tunnelling-data-containing-variables-through-RDF problem are two views of
> the same issue. In both cases, we need to represent to machines the fact
> that we don't know the Web names for various entities, but nevertheless
> know some other things about them. Whether the definition of URI/Resource
> is broad enough to be used for variables is an interesting
> (religious?) question. Reading RFC2396 I'm inclined to suggest that this
> is acceptable:
>
> Excerpted from related thread at
> http://lists.w3.org/Archives/Public/www-rdf-interest/2000Mar/0028.html
> the RFC tells us...
>
> i)      A Uniform Resource Identifier (URI) is a compact string of characters
>         for identifying an abstract or physical resource.
>
> ii)     A resource can be anything that has identity.
>
> and in particular this rather cryptic paragraph:
>
> iii)
>
>          The resource is the conceptual mapping to an entity or set of
>          entities, not necessarily the entity which corresponds to that
>          mapping at any particular instance in time.  Thus, a resource
>          can remain constant even when its content---the entities to
>          which it currently corresponds---changes over time, provided
>          that the conceptual mapping is not changed in the process.
>
> Now this in particular sounds to me a lot like our current problem...
>
> Dan
>
> --
> mailto:danbri@w3.org
Received on Thursday, 4 May 2000 13:53:57 GMT

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