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   Re: Options in XML 1.0

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  • From: Jonathan Borden <jborden@mediaone.net>
  • To: "Simon St.Laurent" <simonstl@simonstl.com>, xml-dev@lists.xml.org
  • Date: Fri, 10 Nov 2000 11:05:35 -0500

Simon St.Laurent  wrote:
> As fond as I have been of DTDs (believe it or not), I think it's well past
> time to extract them from the initial parsing process, and make them a
> post-processing tool, something like schemas.  The document contains
> whatever it contains, and DTD or schema processing is considered an
> addition to the document, not content at the same level as the actual
> document content.

I strongly disagree. In fact there is a role for pre-validation
transformations. DTDs are not merely used for validation and it is this fact
which is causing confusion. I agree that the confusion needs to be
clarified, but I also think we need to clarify the role of DTDs in
pre-validation transformations.

What "pre-validation transformations"? You may exclaim surprise that DTDs
are used in this manner. They are. The most simple 'transformation' is
defaulting of attributes. More complex transformations are performed by the
use of entities (for example, default namespace prefixes ala Modularization
of XHTML and in our ASTM E31.25 Healthcare DTDs see
http://www.openhealth.org/ASTM )

More complex DTD based pre-validation transforms are seen in Architectural
Forms, a DTD based technology. Even more complex transforms can be
accomplished via XSLT. Typically XSLT is seen as a post-validation transform
but suppose an <?xml-stylesheet> PI where to be specified to appear in the
DTD. Such a standard would specify that the DTD be applied after the source
document is passed through the XSLT transform, this would be a
generalization of the ISO Architectural Forms concept.

In any case the current XHMTL, ASTM and HL7 Healthcare DTDs use these DTD
techniques and until XML Schemas can be demonstrated to handle such use
cases: *** including a functional replacement for Architectural Forms as a
pre-validation transformation *** DTDs in their current form are not yet
ready to be put out to pasture, indeed new standards will continue to
specify their use.

Jonathan Borden
The Open Healthcare Group

Co-Chair ASTM E31.25 XML Healthcare DTDs


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