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Re: Issue http://www.w3.org/2000/03/rdf-tracking/#rdf-ns-prefix-confusion

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Wed, 23 May 2001 11:14:14 +0100
To: w3c-rdfcore-wg <w3c-rdfcore-wg@w3.org>
CC: Aaron Swartz <aswartz@upclink.com>
Message-ID: <6318.990612854@tatooine.ilrt.bris.ac.uk>
>>>Aaron Swartz said:

[Hmm, looking at the timestamp, it was sent 3 minutes into our last
meeting :-) ]

> Dave Beckett <dave.beckett@bristol.ac.uk> wrote:
> 
> > 7.  Unprefixed attributes not on The List have no meaning in RDF
> >    and MUST NOT be used to generate statements.   Processors MUST
> >    also skip the element containing such attributes and generate no
> >    statements for the entire XML element and content.
> > 
> > This is to explicitly say what is implict in the the BNF - unprefixed
> > attributes have never been allowed in RDF/XML grammar.  I've gone a
> > bit further to say what to do when they are seen so that there is
> > so consistency in handling them.  This means that all namespace
> > element/attribute prefixing is covered.
> 
> I do not think that this extra step is necessary. Take the innocent mistake:
> 
> <rdf:RDF xmlns:rdf="..." xmlns="..."
> <rdf:Description title="Issues" author="Dave Beckett">
>   <type rdf:resource="http://example.org/#image" />
> </rdf:Description>
> </rdf:RDF>

This is too vague - please fill in the namespace URIs; are they both
to the RDF namespace URI or not?

  Aside: I would ask people give full RDF/XML examples that contain
  URIs and preferably, validated if they are to demonstrate legal
  points - I'm trying hard to do this.  I also don't want RDF/N3 used
  to explain RDF/XML in this forum - it confuses issues and moves the
  discussion to what RDF/N3 means rather than RDF/XML.

Either way, considering 'title' and 'author' - some parsers will
assume they are rdf: concepts due to implementing XML namespaces
wrong (the rdf: on rdf:Description does not pass to the attributes)
and hence could skip the element as it contains unknown RDF
attributes.  Other processors might do all sorts of strange things
creating bare 'title' properties or maybe documentURI#title
properties.

By writing a paragraph like the above, all this is precisely clear -
unprefixed attributes continue to not be allowed.

> 
> The type information is still perfectly valid RDF. ...

the type element is legal but since the outer container is
interpreted differently, there is no guarantee that it would be
processed, since the rdf:Description element might be skipped.

> ... This "skip the element"
> provision was added to ensure forwards compatibility with new
> elements/attributes. Since (I hope that) RDF will not add any more
> attributes which are allowed unprefixed this provision is not necessary.

We already agreed this - there will be no unprefixed attributes in
RDF/XML.

> Also, I too agree with Dan Connolly and would like to see the MUST changed
> to a MAY, so that processors may accept the incorrect version of the
> language for backwards compatibility, but it is not an accepted portion of
> the language.

We discussed that subsequently during the meeting and agreed to make
the stronger deprecation point - deprecated now (SHOULD NOT) and tell
the developers so that they know it will be removed and forbidden
(MUST NOT) at next REC which is probably a year away.

In summary, based on what existing tools do and for consistency, item
7 remains a good answer.

Dave
Received on Wednesday, 23 May 2001 06:14:17 EDT

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