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Re: silly question about rdf:about

From: Sandro Hawke <sandro@w3.org>
Date: Sun, 07 Apr 2002 18:33:47 -0400
Message-Id: <200204072233.g37MXlW09143@wadimousa.hawke.org>
To: Uche Ogbuji <uche.ogbuji@fourthought.com>
cc: www-rdf-interest@w3.org
> > Why is rdf:about treated as magic syntax?  Wouldn't everything work
> > the same in the grammar if
> > http://www.w3.org/1999/02/22-rdf-syntax-ns#about were just another
> > property?
> 
> I now I'm pursuing a cheap form of argument here, but I can't resist likening
> your statement to the old saw: why treat angle brackets as magic syntax?  Why
> not allow the markup language to define the tag delimiters ...

Um, nice try, but languages need magic syntax for separating literal
text from structure.  RDF/XML doesn't need to give rdf:about any magic
status; doing so is just a sometimes-convenient way of thinkings about
things.

> rdf:about is nothing but a convenience for specifying the subject of multiple
> statements in a convenient syntax.  It has no standing whatsoever in the 
> model, or in the concept of the description.  That's the way it should stay.

Without it (and its twin brother rdf:ID), your "node" remains unnamed,
and cannot be merged with another node or otherwise recognized as
meaning anything.  That is, unless you pick some property as the name
property, which is what I'm suggesting.  If you reject the primacy of
rdf:about, rdf:ID, and essentially-identical other unambiguous naming
properties, I don't see how you can use RDF for much of anything.
(Since I know you do use RDF for lots of things, I assume there's some
misunderstanding here!)

> If one doesn't like it, there is always N3.

*shrug*.   Once one understands how to reify N3 formulas, N3 and
RDF/XML are the same, except that you can't serialize some RDF graphs
in RDF/XML.   (that is, unless we introduce the trick below....)

> And actually, it would be nice to get a standard straight triple XML 
> serialization for RDF.  I think Jonathan Borden once posted the obvious 
> approach.  Any reason not to make this official in some way?

I can't find Jonathan's, but it seems to me that a clear & simple XML
syntax for RDF would turn out to just be an assertion of reified RDF.
That is, we define, rdf:Assertion as a subclass of rdf:Statement, and
then we can choose to transmit RDF as

  <rdf:RDF>
     <rdf:Assertion>
        <rdf:subject rdf:resource="...some URI-Reference..." />
        <rdf:predicate rdf:resource="...some URI-Reference..." />
        <rdf:object rdf:resource="...some URI-Reference..." />
     </rdf:Assertion>
  </rdf:RDF>

[each of those three properties could have had a literal value instead.]

This structure has the advantage of allowing serializations that the
traditional RDF/XML syntax prohibits.   All it requires beyond RDF M&S
is the definition of rdf:Assertion as a subClass of rdf:Statement
which has the semantics that any assertion described must be taken to
be as true as the description.

> If we had such, it would be another way to avoid distraction by serialization
> details.

I'm with you on that.    But some people ARE very focussed on the
details of the RDF/XML syntax, and I thought I would nudge them a
little more towards simplicity.

    -- sandro
Received on Sunday, 7 April 2002 18:36:41 GMT

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