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rdf:parseType="Literal" and XML Fragment interchange

From: Dan Connolly <connolly@w3.org>
Date: Thu, 16 Aug 2001 09:54:18 -0500
Message-ID: <3B7BDE9A.53D892A7@w3.org>
To: www-xml-fragment-comments@w3.org
CC: w3c-rdfcore-wg@w3.org
RDF syntax has a mechanism[1] for saying "here's a hunk
of XML to be used as the value of a property"; implementors
have raised issues with the way it's specified[2,3].

[2]  http://www.w3.org/2000/03/rdf-tracking/#rdfms-xmllang
[3] 
http://www.w3.org/2000/03/rdf-tracking/#rdfms-literal-is-xml-structure

At a recent FTF meeting[4], it seemed that the XML Fragments
spec might provide a solution to these issues, but we weren't
sure how.

Would you (the fragments editors) please take a look at the
example in [1] below? I'd like to know what it would
look like if you took the contents of the dc:Title
element and wrapped it per the XML Fragment interchage
spec.

Could the result take the form of a string (character sequence)
that, when parsed per the fragments spec, gives back
all the relevant information, like namespaces, xml:lang, etc?


[1]

[[[
7.5. Values Containing Markup

When a property value is a literal that contains XML markup, the
following
syntax is used to signal to the RDF interpreter not to interpret the
markup but
rather to retain it as part of the value. The precise representation of
the
resulting value is not specified here.

In the following example, the value of the Title property is a literal
containing
some MATHML markup.

<rdf:Description
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:dc="http://purl.org/metadata/dublin_core#"
  xmlns="http://www.w3.org/TR/REC-mathml"
  rdf:about="http://mycorp.com/papers/NobelPaper1">

  <dc:Title rdf:parseType="Literal">
    Ramifications of
       <apply>
      <power/>
      <apply>
        <plus/>
        <ci>a</ci>
        <ci>b</ci>
      </apply>
      <cn>2</cn>
    </apply>
    to World Peace
  </dc:Title>
  <dc:Creator>David Hume</dc:Creator>
</rdf:Description>
]]]

--        Resource Description Framework (RDF) Model and Syntax
Specification
http://www.w3.org/TR/REC-rdf-syntax/
Wed, 24 Feb 1999 14:45:07 GMT

[4]
========
excerpt from http://www.w3.org/2001/sw/RDFCore/20010801-f2f/

#rdfms-literal-is-xml-structure

log

It was suggested that there had been basic agreement on the mailing
list, that
literals with a parseType of "Literal" would be treated as strings, but
the model
would contain further information. There are many details to work out,
but this
is the basic principle. A list of components that would have to be in
the model
was started:

     the string 
     parseType (string or QName) 
     namespaces 
     language 
     base URI 
     entities 

A number of different approaches were identified:

     the XML in the input document must be self sufficient (an
incomplete
     solution) 
     parser adds namespaces (an incomplete solution) 
     replace the literal with an infoset representation of RDF 
     serialise the infoset to a string 
     use XML fragments 
     deprecate and represent as CDATA 

It was suggested that parseType="Literal" could be dropped but Ron
Daniel and
Eric Miller spoke up that there are users who use it. It was suggested
that the
parser adding namespace definitions to the literal might break an XML
signature. Concern was raised over entities in the literal. The
existence of the
xml fragments work was noted.

=========


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 16 August 2001 10:54:20 EDT

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