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Re: #rdfms-difference-between-ID-and-about

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Fri, 15 Jun 2001 15:58:07 -0700
Message-ID: <3B2A92FF.60CA6705@db.stanford.edu>
To: Dan Connolly <connolly@w3.org>
CC: guha@alpiri.com, Aaron Swartz <aswartz@upclink.com>, Brian McBride <bwm@hplb.hpl.hp.com>, rdf core <w3c-rdfcore-wg@w3.org>
Currently, the concept of relative URIs is present in the M&S 1.0
serialization syntax only, and is not reflected in the model in any way.
That is, relative URIs is a just another "abbreviation feature" of the
M&S syntax, and I'd like to emphasize that in the revised spec to avoid
misconceptions. As abbreviation features, relative URIs have nothing to
do with the fragment IDs described in
http://www.w3.org/DesignIssues/Model.html#Fragement (for example, a
fragment ID in an RDF document does *not* refer to a portion of this
document). Therefore, IMO the axioms and benefits summarized by TimBL
for HTML at above link do not seem to hold in the RDF world.

I feel strongly about not using relative URIs, especially given the
parsing/editing complication (see prev. postings in this thread), and
the problems associated with moving RDF documents from one location to
another. However, I think keeping cleaned-up rdf:ID, rdf:about and
relative URIs in the revised M&S syntax is essential for backward
compatibility and is the least bloody compromise (sigh...) I'd just
suggest to word it so the developers understand the pros and cons.


Dan Connolly wrote:
> "R.V.Guha" wrote:
> >
> > Ok, Aaron, you hit the nail on the head.
> >
> > RDF absolutely has to make sense even outside the context of
> > an enclosing document which can be given a uri. so ...
> So... what? That doesn't make any sense to me.
> An RDF document is an XML document. Each XML document
> has a base URI (cf the infoset spec).
> If you copy the contents from one
> place in the web to another, you get a different XML
> document, and hence a difference RDF document; if
> it uses relative URI references, the resulting triples
> may be different.
> This is by design.
> This design does allow users to goof,
> but it also allows folks to manage collections of
> documents and by and large, it has succeeded over the course
> of the last 10 years.
> Noone is forced to use relative URI references; anyone
> who uses them does so by choice. Surely the consequences
> of that choice for RDF documents should be the same
> as the consequences for HTML, XML, PDF,
> and other document formats in the Web, no?
> Or rather: surely the the consequences *are* the same for
> RDF as for XML in general; we're not designing RDF 1.0 today;
> we're just clarifying the spec; and the spec is already
> pretty clear on this:
>   [[[ The value of the about attribute is interpreted as
>   a URI-reference per Section 4 of [URI]. The corresponding
>   resource identifier is obtained by resolving the
>   URI-reference to absolute form as specified by [URI].
>   ]]]
>   --        Resource Description Framework (RDF) Model and Syntax
> Specification
>   http://www.w3.org/TR/REC-rdf-syntax/
>   Wed, 24 Feb 1999 14:45:07 GMT
> The only question is about this sort of fuzzy text:
>   [[[ The ID attribute signals the creation of a new resource ... ]]]
> But this text in particular suggests pretty strongly
> that rdf:ID="foo" means the same thing as rdf:about="#foo" :
>   [[[ The ID attribute, if specified, provides the URI
>   fragment identifier for c.
>   ]]]
>   -- section 6. Formal Grammar for RDF
> --
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 15 June 2001 18:32:02 UTC

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