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URIrefs and granularity - cont.

From: Jeroen Bekaert <jbekaert@lanl.gov>
Date: Mon, 7 Jul 2003 16:41:51 -0600
Message-ID: <000a01c344d8$f58f9bc0$7f0aa580@northernoriole>
To: <www-rdf-interest@w3.org>

Hi All,

2 weeks ago, I have posted the message included below. Until now, there was
no reply to this message.  Therefore,  I repost the message, hoping that
someone will give us his/her (brief) opinion about this issue.

Thanks in advance
jeroen bekaert
Los Alamos National Laboratory

---------------------------------------->

Hi All,

in addition to my previous emails concerning the removal of the aboutEach
attribute in the current RDF spec., I have the following questions I would
like to discuss with you.

Suppose I have a statement consisting of:
1. a subject, identified by: http://foo/foo.xml#xpointer(Item[position() = 4
or  position() = 5])
2. a property: dc:author
3. an object: "John Doe"

Then the RDF/XML syntax looks as follows:

<?xml version="1.0"?>
<rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#
xmlns:dc="http://purl.org/dc/elements/1.1/">
  <rdf:Description rdf:about=http://foo/foo.xml#xpointer(Item[position() = 4
or  position() = 5])"/>
    <dc:author>John Doe</dc:author>
  </rdf:Description>
</rdf:RDF>

As you might notice, the subject resource-identifier refers to 2
subcomponents of the containing resource, namely an Item with position() = 4
and an Item with position() =5. This way, our proprerty is attached to both
the subcomponents of the resource http://foo/foo.xml. The extent of the
subcomponent is defined by the fragment identifier in conjunction with the
content type of the containing resource (i.e., text/xml). As such, in our
case, the fragment identifier is an XPointer.

So, in my opinion, according to the technical spec. of RDF, this statement
is perfectly valid. However, I do have some concerns about the sematic
meaning of it. The above-mentioned example is stating the following:
(UNION of (http://foo/foo.xml#Item[4], http://foo/foo.xml#Item[5])) has a
property dc:creator with value "John Doe".

Now, one could argue if it also follows that:
http://foo/foo.xml#Item[4] has property dc:creator with value "John Doe"
http://foo/foo.xml#Item[5] has property dc:creator with value "John Doe"

In a more general case, one could come up with the following example:
Let's assume we have a subject resource-identifier pointing to an XML file.
1. a subject: http://foo/foo.xml
2. a property: dc:author
3. an object: "John Doe"

Then the RDF/XML syntax looks as follows:

<?xml version="1.0"?>
<rdf:RDF xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#
xmlns:dc="http://purl.org/dc/elements/1.1/">
  <rdf:Description rdf:about=http://foo/foo.xml/>
    <dc:author>John Doe</dc:author>
  </rdf:Description>
</rdf:RDF>

The xml document that I am pointing at looks like:

<foo>
    <bar1>test1<bar1>
    <bar2>test><bar2>
</foo>

Does this mean that John Doe is also the creator of <bar1> and <bar2>?
According to, among others, Berners Lee
(http://www.w3.org/DesignIssues/Identity.html), the identifier refers to the
total object described by the node, in RDF terms the 'resource'.
Consequently, the property does also address every part of that resource.


Does this make any sense?


Kind regards,
Jeroen Bekaert

Digital Library Research and Prototyping team
Los Alamos National Laboratories
PO Box 1663, MS P362
Los Alamos, NM, 87545, USA
tel. +1 (505) 664 0580
Received on Monday, 7 July 2003 18:42:49 GMT

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