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a simpler form of rdf xml

From: Henry Story <henry.story@bblfish.net>
Date: Thu, 13 Jan 2005 03:02:01 +0100
Message-Id: <1D2F1994-6507-11D9-8C94-000A95D9FA7A@bblfish.net>
Cc: atom-owl@googlegroups.com
To: www-rdf-interest@w3.org

Tim Bray, Roy Fielding and other have recently made some interesting
comments on the atom list saying that xml's tree structure has an 
implicit
semantics.

This has led me to the following thought. Perhaps there is a default
mapping from xml to triple space that encodes xml such as

<feed atom:version="draft-ietf-atompub-format-03: do not deploy"
       xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-03">
      <head>
        <title>Example Feed</title>
        <link href="http://example.org/"/>
        <updated>2003-12-13T18:30:02Z</updated>
        <author>
          <name>John Doe</atom:name>
        </author>
      </head>
    <entry>
        <title>Atom-Powered Robots Run Amok</title>
        <link href="http://example.org/2003/12/13/atom03"/>
        <id>vemmi://example.org/2003/32397</id>
        <versionid>vemmi://example.org/2003/32397/v1</versionid>
        <updated>2003-12-13T18:30:02Z</updated>
      </entry>
  </feed>

this way:

_f --feed--->_f1
              |---head--->_h1
              |           |---title-->"example Feed"
              |           |---link--->_l1
              |           |             |--href----> 
<http://example.org/>
              |           |--updated->"2003-12-13T18:30:02Z"
              |           |--author-->_a1
              |                       |---name--->"John Doe"
              |                       |---mbox--->"john@doe.com"
              |--entry-->_e1
                         |--title-->"Atom Powered Robots Run Amok"
                         |--link--->_l1
                         |          |--href-----> 
<http://example.org/2003/12/13/atom03>
                         |--id-------> 
<vemmi://example.org/2003/12/13/atom03>
                         |-versionid-> 
<vemmi://example.org/2003/12/13/atom03/v1>
                         |--updated-->"2003-12-13T18:30:02Z"


The method of producing the mapping is very simple. Every element has a 
blank element
as subject and a blank element as a node, unless the child of the node 
is a simple string.
Every attribute on an element is an attribute on the blank node that 
that element points to,
and has as object the interpretation of the string required for that 
attribute.

So in the example above the subject of the "head" element is  the blank 
node
_f1 and the object is the blank node _h1. Take the "link" element

    <link href="http://example.org/"/>

it has a blank node _h1 as subject and a blank node _l1 as object. The 
attribute
atom:href has the blank node _l1 as subject and the interpretation of 
"http://example.org"
that it requires as object.

Good so how do we know what that interpretation is? Well we have to 
look to the
ontology of the atom:href attribute. Perhaps we have a file at hand 
that gives
us this. This file says the object of href is a resource. So we cast 
that to a
resource, and we get what we were asking for above.

Interestingly enough the triple model I get from parsing the
above xml that way is (nearly) exactly the same as the triple model
I get from parsing the closest rdf/xml I could get that resembles
the xml above:

<?xml version="1.0" encoding="utf-8"?>
    <atom:feed atom:version="draft-ietf-atompub-format-03: do not deploy"
     xmlns:atom="http://purl.org/atom/ns#draft-ietf-atompub-format-03"
     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
      <atom:head rdf:parseType="Resource">
        <atom:title>Example Feed</atom:title>
        <atom:link atom:href="http://example.org/"/>
        <atom:updated>2003-12-13T18:30:02Z</atom:updated>
        <atom:author rdf:parseType="Resource">
          <atom:name>John Doe</atom:name>
        </atom:author>
      </atom:head>
    <atom:entry rdf:parseType="Resource">
        <atom:title>Atom-Powered Robots Run Amok</atom:title>
        <atom:link atom:href="http://example.org/2003/12/13/atom03"/>
        <atom:id>vemmi://example.org/2003/32397</atom:id>
        <atom:versionid>vemmi://example.org/2003/32397</atom:versionid>
        <atom:updated>2003-12-13T18:30:02Z</atom:updated>
      </atom:entry>
    </atom:feed>

So that would tend to indicate that we are close to the intuitions of 
the original
developers of rdf/xml.

Now how do we ever get to fill in the blank nodes that are so 
plentifully spread around?
Well again with the help of the ontology, and especially properties 
that are both functional,
inverse functional, symmetric and transitive: ie: identity properties.

So if for example the versionid property were such an identity property 
then we could
deduce from the above graph the following graph:


_f --feed--->_f1
              |---head--->_h1
              |           |---title-->"example Feed"
              |           |---link--->_l1
              |           |             |--href----> 
<http://example.org/>
              |           |--updated->"2003-12-13T18:30:02Z"
              |           |--author-->_a1
              |                       |---name--->"John Doe"
              |                       |---mbox--->"john@doe.com"
              |--entry--> <vemmi://example.org/2003/12/13/atom03/v1>
                             |--title-->"Atom Powered Robots Run Amok"
                             |--link--->_l1
                             |          |--href-----> 
<http://example.org/2003/12/13/atom03>
                             |--id-------> 
<vemmi://example.org/2003/12/13/atom03>
                             |--updated-->"2003-12-13T18:30:02Z"


This oddly enough still leaves a problem with xml like the following

<entry>
    <generator
        uri="https://bloged.dev.java.net/"
        version="0.5">BlogEd</generator>
</entry>

which is exactly the same type of xml that does not seem to be parsable 
in rdf-xml

perhaps that should be

_e1
  |------generator---->_g ---rdf:text-->"BlogEd"
                        |----uri---> <https://bloged.dev.java.net/>
                        |--version-> "0.5"
  
                       
Received on Thursday, 13 January 2005 02:02:05 GMT

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