Re: [xml-dev] Defining an XML Fragment in W3C Schema

[ht@cogsci.ed.ac.uk (Henry S. Thompson)]

"Chiusano Joseph" <chiusano_joseph@bah.com> writes:

> I have a need to define an XML fragment in a W3C schema. In other words,
> an element or attribute in the schema should be able to contain an XML
> fragment, with the parser recognizing this XML fragment as actual data
> rather than part of the XML document.
> 
> I've researched XML Fragments, and I also understand that CDATA was part
> of the W3C Schema specification at one point but did not make it into
> the final version.  Can anyone please suggest a way to accomplish this?
> 
> Much appreciated,

Not sure I understand, but I'll try.

You want an element to be constrained to contain a quoted XML
fragment.  So the following is OK:

<root>
<fragmentContainer>
&lt;?xml version='1.0'?&gt;
&lt;doc/&gt;
</fragmentContainer>
</root>

But the following is not:

<root>
<fragmentContainer>
&lt;?xml version='1.0'?&gt;
garbage
</fragmentContainer>
</root>

Is that it?

In which case, _mirabile dictu_, the best you can do is use a
NOTATION, along the following lines

<xs:notation name="XML_10_2e"
             public="-//W3C//NOTATION XML 1.0//EN"
             system="http://www.w3.org/TR/2000/REC-xml-20001006"/>

<xs:element name="fragmentContainer">
 <xs:complexType>
  <xs:simpleContent>
   <xs:extension base="xs:string">
    <xs:attribute name="fragType" fixed="XML_10_2e">
     <xs:simpleType>
      <xs:restriction base="xs:NOTATION">
       <xs:enumeration value="XML_10_2e"/>
      </xs:restrition>
     </xs:simpleType>
    </xs:attribute>
   </xs:extension>
  </xs:simpleContent>
 </xs:complexType>
</xs:element>
  
Note that because XML Schema works on infosets, not character strings,
there's now way it could have defined something equivalent to SGML's
CDATA, even if it had wanted to.  So for direct inclusion of a quoted
XML fragment, you need to use either &lt; etc. or <![CDATA[ .... ]]>
_in your instance_.

XInclude provides a way to include an XML fragment as text.

Hope this helps.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                      Half-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
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