W3C home > Mailing lists > Public > www-tag@w3.org > November 2002

Re: Another RDDL/RDF proposal

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Date: Wed, 13 Nov 2002 11:00:31 +0000
To: Jonathan Borden <jonathan@openhealth.org>
Cc: WWW-Tag <www-tag@w3.org>
Message-ID: <6790.1037185231@hoth.ilrt.bris.ac.uk>

>>>Jonathan Borden said:
> What I want to do is this:
> 
> <rddl:description rdf:parseType="Literal" rdf:datatype="&xhtml;Flow.mix"
>         xmlns="&xhtml;">
>     <h1>Some typed XML</h1>
>     <p>This is an example of typed XML. It is intended to validate according
> to xhtml:Flow.mix. Now if RDF allowed this I might actually have a prayer of
> writing a document that could be RDF and which I could incorporate valid
> snippets of RDF, e.g. fragements of XHTML.
>     </p>
>     <p><b>Perhaps you have a different solution to this use case.</b></p>
> </rddl:description>
> 
> However this isn't legal RDF as you don't allow typed XML literals.

We do.  RDF typed literals are a pair of
  (datatype URI-ref, unicode string lexical form)  [ignoring lang for now]
  -- http://www.w3.org/TR/rdf-concepts/#dfn-typed-literal
and we defined a single datatype URI-ref for lexical forms that are
of the XML literal type, rdfs:XMLLiteral.

In the RDF/XML, rdf:parseType="Literal" attribute is a synonym for
rdf:datatype="&rdfs;XMLLiteral" plus it makes the parser allow any
XML element content inside the element, since the parser is an XML
parser.  I'm assuming the latter is what you care about.

The question is always, what does it look like in the RDF graph,
written as triples?  Here you have two slots to fill as the object
typed literal node (datatype URI-ref, unicode string lexical form)

It is certainly possible that we could allow rdf:parseType="Literal"
to generate that lexical form for you (from serialization of the XML
infoset of the content), and rdf:datatype to give you the
URI-reference.

However, would you be surprised if the serialization of such a triple
to a new RDF/XML file, gave you this?

 <rddl:description rdf:datatype="&xhtml;Flow.mix">
     &lt;h1 xmlns="&xhtml"&gt;Some typed XML&lt;/h1&gt;
     &lt;p xmlns="&xhtml"&gt;This is an example of typed XML. It is intended to validate according
 to xhtml:Flow.mix. Now if RDF allowed this I might actually have a prayer of
 writing a document that could be RDF and which I could incorporate valid
 snippets of RDF, e.g. fragements of XHTML.
     &lt;/p&gt;
     &lt;p xmlns="&xhtml"&gt;&lt;b&gt;Perhaps you have a different solution to this use case.&lt;/b&gt;&lt;/p&gt;
 </rddl:description>

(I'm faking this somewhat, you might have to expand the xmlns URIs,
it might also have to be canonicalized XML)

This is because the indication that this came from a
rdf:parseType="Literal" type syntax, is not recorded in the RDF typed
literal.  It would need an extra isXML flag, and a subsequent change
to the RDF model so that every (typed) literal had that flag.

Dave
Received on Wednesday, 13 November 2002 06:03:56 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 26 April 2012 12:47:12 GMT