xmlhack: The RDDL Challenge

On behalf of the W3C TAG, Tim Bray asked the XML community for examples of what documentation at the end of a namespace should look like, using RDDL (Resource Directory Description Language) as a starting point. Several interesting alternatives have been proposed.

The challenge was to describe a vocabulary based on XHTML that would be able to express a few basic pieces of information:

There's a namespace whose name is "http://example.com/L". It has a relationship to a RelaxNG schema:

at "http://example.com/schemas/L.rng"
with nature "http://relaxng.org/ns/structure/1.0"
with purpose "http://www.rddl.org/purposes#validation"

It has a relationship to a CSS stylesheet:

at "http://example.org/style/L.css"
with nature "http://www.isi.edu/in-notes/iana/assignments/media-types/text/css"
with purpose "http://www.rddl.org/purposes#render"

Bray himself led off with an initial proposal, a straightforward mapping of specialized elements, not making special use of XLink or RDF.

<body><h1>The L Namespace</h1>
<p>The name of the namespace is
    "http://example.com/L" </p>
<rddl:rr href="/schemas/L.rng"
          title="RelaxNG Schema"
          nature="http://relaxng.org/ns/structure/1.0"
          purpose="http://www.rddl.org/purposes#validation" />
<rddl:rr href="/style/L.css"
          title="CSS Stylesheet"
          nature="http://www.isi.edu/in-notes/iana/assignments/media-types/text/css"
          purpose="http://www.rddl.org/purposes#render" />
</body>

Chris Wilper next responded, using the RPV syntax that Tim Bray had earlier proposed.

<head>
  <RPV xmlns="http://www.rdf.net/rpv/">
    <R>
      <PV p="http://www.rddl.org/#resource" 
            v="/schemas/L.rng"/>
      <PV p="http://www.rddl.org/#resource" 
            v="/style/L.css"/>
      </R>
      <R r="/schemas/L.rng"/>
        <PV p="http://www.rddl.org/#title" 
            v="RelaxNG Schema"/>
        <PV p="http://www.rddl.org/#nature" 
            v="http://relaxng.org/ns/structure/1.0"/>
        <PV p="http://www.rddl.org/#purpose" 
            v="http://www.rddl.org/purposes#validation"/>
      </R>
      <R r="/style/L.css"/>
        <PV p="http://www.rddl.org/#title" 
            v="CSS Stylesheet"/>
        <PV p="http://www.rddl.org/#nature" 
            v="http://www.isi.edu/in-notes/iana/assignments/media-types/text/css"/>
        <PV p="http://www.rddl.org/#purpose" 
            v="http://www.rddl.org/purposes#render"/>
      </R>
    <RPV>
  </head>

Jonathan Borden proposed an RDF-compatible variation of Tim's proposal.

<body><h1>The L Namespace</h1>
<p>The name of the namespace is
    "http://example.com/L" </p>

<rddl:resource rddl:title="RelaxNG Schema">
    <rddl:href rdf:resource="/schemas/L.rng"/>
    <rddl:nature rdf:resource="http://relaxng.org/ns/structure/1.0" />
    <rddl:purpose rdf:resource="http://www.rddl.org/purposes#validation" />
</rddl:resource>
<rddl:resource rddl:title="CSS Stylesheet">
    <rddl:href rdf:resource="/style/L.css"/>
    <rddl:nature
rdf:resource="http://www.isi.edu/in-notes/iana/assignments/media-types/text/
css" />
    <rddl:purpose rdf:resource="http://www.rddl.org/purposes#render" />
</rddl:resource>
</body>

Tim Berners-Lee put up a web page citing a number of examples using RDF along with some discussion.

Most recently, Micah Dubinko proposed a slight modification to XHTML 2.0 that would make it powerful enough to fulfill the challenge with no additional vocabulary. The proposal added two changes to the tag, an 'about' attribute and nesting.

<head>

<link rel="schema.rddl" href="http://rddl.org" />


<meta about="http://example.com/L" name="rddl.related">
  <meta name="rddl.location">
    http://example.com/schemas/L.rng
  </meta>
  <meta name="rddl.nature">
    http://relaxng.org/ns/structure/1.0
  </meta>
  <meta name="rddl.purpose">
    http://www.rddl.org/purposes#validation
  </meta>
</meta>

<meta about="http://example.com/L" name="rddl.related">
  <meta name="rddl.location">
    http://example.org/style/L.css
  </meta>
  <meta name="rddl.nature">
    http://www.isi.edu/in-notes/iana/assignments/media-types/text/css
  </meta>
  <meta name="rddl.purpose">
    http://www.rddl.org/purposes#render
  </meta>
</meta>
...
</head>

Additional submissions can be mailed to www-tag@w3.org.