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

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Thu, 14 Jun 2001 12:28:35 -0700
Message-ID: <3B291063.2CF65749@db.stanford.edu>
To: Brian McBride <bwm@hplb.hpl.hp.com>
CC: guha@alpiri.com, rdf core <w3c-rdfcore-wg@w3.org>
Brian McBride wrote:
> 
> Sergey Melnik wrote:
> 
> > With respect to this and other syntax issues, I'd like to remind of the
> > "roundtrip" test, which have been raised many times on RDF Interest: an
> > RDF tool must be able to parse, serialize, parse, serialize etc. without
> > loss of information, i.e., on every parse, exactly the same set of
> > statements is produced. Notice that after the first parse, rdf:ID will
> > be necessarity replaced by rdf:about, since the model does not
> > intrinsically capture the information about its origin.
> 
> If
>   <rdf:Description rdf:ID="foo"/>
> 
> is defined to be equivalent to, i.e. represents the same triples as:
> 
>   <rdf:Description rdf:about="#foo"/>
> 
> and the round tripping test is defined to be that XML/RDF before
> represents the same triples as the XML/RDF after (i.e. model
> equivalence) which I think is the test that you suggest,
> then this solution passes the round triping test.
> 
> Brian

This is right. However, by endorsing rdf:ID and rdf:about with relative
anchors we embark on potentially unpleasant issues like e.g. HTTP
redirect, support in RDF editors etc. In HTTP redirect, we'll need to
specify precisely which URL will be assigned for the namespace, the
original one, or the resolved one. Furthermore, if you are using an RDF
editor, it has to maintain an additional flag with each "local" resource
plus the URL of the page. This distinction becomes essential when you
want to store the content at another URL and assert that it "moved from
<previous URL>". If the editor cannot distinguish relative and absolute
references, it will blindly replace <previous URL> with a relative
reference resolving to the new page. Moreover, if the distinction
between relative and absolute URLs is required, the parsers will need to
support it as well.

I'm trying to make a point that this issue is closely related to
http://www.w3.org/2000/03/rdf-tracking/#rdf-ns-prefix-confusion, which
has been resolved in favor of "in doubt be precise".

Sergey
Received on Thursday, 14 June 2001 15:15:43 EDT

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