On Monday, October 01, 2001 14:23 Alan Stockdale wrote
Subject: Re: QDML/QDDL?
...
> One other thought: I'm not an XML expert but aren't DTD's old hat?
> Aren't we really talking about XML Schemas? I quote from a recent
> W3 document (See: http://www.w3.org/TR/xmlschema-1/): "XML
> Schema: Structures specifies the XML Schema definition language,
> which offers facilities for describing the structure and constraining
> the contents of XML 1.0 documents, including those which exploit
> the XML Namespace facility. The schema language, which
> is itself represented in XML 1.0 and uses namespaces, substantially
> reconstructs and considerably extends the capabilities found in XML
> 1.0 document type definitions (DTDs)."
Use of emerging capabilities such as XML Schemas and Namespaces could
provide critical features such as making the standard more adaptable and
extensible (thereby avoiding the need to codify all details for all
users) while also providing templates and other scaffolding for users.
DDI may be heading there (see quoted material below).
Regards,
John Hanna
----------------------------------
DDI Evaluation Report
see http://www.icpsr.umich.edu/DDI/codebook/papers/evalsummary.doc
quote1...
5. Appropriateness of technical Format - XML and DTDs, and availability
of tools and applications
One of the great challenges of the DDI effort is the rapid evolution of
the enabling infrastructure that underlies their efforts - initially
SGML, more recently XML and its many sub-parts. The state of the
current effort is about as sensible as it can be in light of this
ongoing technological shift. The use of XML is the only sensible thing
one could do. any other approach would be seriously flawed. The use of
DTDs is less clear. The ICPSR team is well aware of the existing
options - DTDs, XML Schemas, RDF Schemas, and continues to explore them.
DTDs are stable and a known approach, but have a significant liability
(they are difficult to extend or modularize). Plans for Version 2 of
the DDI standard are exploring the options for overcoming this
liability.
quote2...
The XML DTD was the appropriate choice at the time the decision was made
to use it. It is still the best available choice today. Other, perhaps
better, choices may become available soon. These include
XML Schema (http://www.w3.org/TR/xmlschema-0/) and
Resource Description Framework ("RDF"
see http://www.w3.org/TR/rdf-schema/). Because these are still in draft
form and because their intents overlap, it is not yet time to adopt
either.
One of the reasons that XML in general is the right standard to use is
that whatever work is done on the DTD and in marking up documentation
using the DDI will not be wasted when new standards emerge.
Transferring to new technologies will be (relatively) easy and the
markup itself should be compatible with future standards.
----------------------------------
|