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Re: How/Why to implement Reification efficiently...

From: Stefan Kokkelink <skokkeli@mathematik.uni-osnabrueck.de>
Date: Mon, 04 Dec 2000 14:05:45 +0100
Message-ID: <3A2B96A9.41938E2C@mathematik.uni-osnabrueck.de>
To: Ora Lassila <daml@lassila.org>
CC: Pierre-Antoine CHAMPIN <champin@bat710.univ-lyon1.fr>, www-rdf-interest@w3.org
Ora, thank you for this clear statement!
I am going to implement it in the next release
and I  hope other parsers will implement it, too.
(At the moment this must be considered as a bug in
all parsers available online, including my own).

I think the clarification of some aspects of the
syntax is crucial for the development of software
for RDF.

Hence I would like to ask two more
questions:

1. How is the following XML expected to be parsed:

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:s="http://description.org/schema/">
  <rdf:Bag ID="BAG_ID">
     <rdf:li resource="xyz"/>
     <rdf:li resource="abc"/>
  </rdf:Bag>
 <rdf:Description aboutEach="#BAG_ID">
      <s:creator rdf:ID="Stat_ID">Karl</s:creator>
      <!--       ^^^^^^^^^^^^^^^^   -->
</rdf:Description>
</rdf:RDF>

According to the BNF the rdf:ID attribute of s:creator
is allowed. But this doesn't make sense to me, since 
a reified statement must exactly have one subject,property
and object. 

2. This thread  started with the question if an rdf:Description
element always leads to  a Bag containing the refied statements.
M&S says:
'The Description element itself represents an instance of a Bag
resource. The members of this Bag are the resources corresponding to the
reification of 
each of the statements in the Description. If the bagID attribute is 
specified its value is the identifier of this Bag, else the Bag is
anonymous.'

But this Bag is missing in all the examples of M&S, unless
a BagID is stated explicitly.

What is a parser expected to do?

Stefan


Ora Lassila wrote:
> 
> Pierre-Antoine CHAMPIN wrote:
> > rdf:aboutEach allows to distribute a property over many subjects,
> 
> Correct. This is exactly the intended purpose of "aboutEach".
> 
> > why would it not be possible to distribute a property over many objects.
> 
> It would, but it is not part of the RDF M+S. If this discussion is about
> how we should *interpret* RDF M+S, then this does not work. If we are
> discussing additions/modifications to RDF M+S, then why not.
> 
>         - Ora
> 
> --
> Ora Lassila <daml@lassila.org> +1 (781) 993-4603
Received on Monday, 4 December 2000 08:06:50 GMT

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