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Re: Call for agenda items

From: Dan Brickley <danbri@w3.org>
Date: Thu, 6 Nov 2003 06:20:30 -0500
To: Dave Beckett <dave.beckett@bristol.ac.uk>
Cc: Graham Klyne <gk@ninebynine.org>, Jeremy Carroll <jjc@hplb.hpl.hp.com>, w3c-rdfcore-wg <w3c-rdfcore-wg@w3.org>
Message-ID: <20031106112028.GH24890@w3.org>

Perhaps the simplest clarification that would fix rdf:Alt is to make it 
clear that it needs to be used with supporting vocabulary, ie. this is a 
modelling level component of RDF, something that can be used, rather
than something down deep in the RDF infrastructure.

ie. I can't write

<foaf:Person>
  <foaf:workplaceHomepage>
    <rdf:Alt>
      <rdf:li>
       <foaf:Document rdf:about="http://www.w3.org/"/>
      </rdf:li>
      <rdf:li>
       <foaf:Document rdf:about="http://ilrt.org/"/>
      </rdf:li>
    </rdf:Alt>
  </foaf:workplaceHomepage>
</foaf:Person>

...and to expect it "just work" by the power of RDF.

If foaf:Document and rdf:Alt are disjoint (which FOAF could state in
OWL) this would be false, since foaf:workplaceHomepage has a range of
foaf:Document.

I guess the best practice guideline is that rdf:Alt is only useful when 
used alongside RDF vocabulary explicitly created to work with it.

eg. a foaf:workplaceHomepageAlt property with rdf:Alt as its value would 
be OK.

Would the primer be a natural home for something like this? Or maybe 
just shove it in the ESW wiki...?

Dan

* Dave Beckett <dave.beckett@bristol.ac.uk> [2003-11-06 11:09+0000]
> 
> On Thu, 06 Nov 2003 10:41:44 +0000, Graham Klyne <gk@ninebynine.org> wrote:
> 
> > 
> > At this stage of the game, if we choose to make any substantive changes in 
> > response to these comments I think they should be simple excisions.
> > 
> > I could see removing the preference for the first Alt as an excision.  Or 
> > simply removing Alt all together?  There's nothing special about rdf:Alt 
> > that users couldn't define their own vocabulary for it.  (Personally, I 
> > think Alt is rather like the human appendix:  of little practical value and 
> > a potential source of inflammation.)
> 
> We already decided not to change RDF containers, I don't see any point
> doing that further now - it is not a critical change.
> 
> RDF Semantics says on Alt:
> "things of type rdf:Alt are considered to represent a collection of
> alternatives, possibly with a preference ordering"
> -- 3.2.2 http://www.w3.org/TR/rdf-mt/#Containers
> 
> RDF Concepts & AS WD says nothing.
> RDF/XML WD deals with the syntax use only.
> 
> RDF Primer does mention the prefered value rdf:_1
> 
> "An Alt container is intended to have at least one member, identified by
> the property rdf:_1. This member is intended to be considered as the
> default or preferred value. Other than the member identified as rdf:_1,
> the order of the remaining elements is not significant."
> -- just after http://www.w3.org/TR/rdf-primer/#example15
> 
> Maybe there is some work to make these a little more aligned.
> 
> Dave
Received on Thursday, 6 November 2003 06:20:55 EST

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