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Hello Paul,
Paul said:
> Please give a concrete example where you have run into these
> limitations.
Didier replies:
With pleasure. To give you the exact query is beyond the limits of my memory
but I can explain the difficulties I encountered. When I wanted to obtain a
particular document from an Oracle DB using the XDK[1] to be included with
the XSLT document function, this ended with the limitations of the actual
"document" function limitations. The XDK allows you to create sophisticated
queries with a domain language Oracle created. We can perceive this language
as a sql superset allowing us to create hierarchies from a system storing
arrays (i.e tables). Moreover their domain language allows to specify a
template describing the overall structure the returned XML document should
take. Their domain language is very powerful, well documented, etc... bottom
line I couldn't fetch a document created with their domain language and use
it in my style sheet to convert it into another domain language (i.e. a
rendering language).
Several groups are creating new domain languages based on XML. This is
precisely the vocation of XML (since it is a meta language that can could be
used to create domain languages). To include an XML document inside a URL is
beyond the limits of URLs. This is a serious limitation for several elements
of the XML framework. And if we say to the people to stop creating query
languages (a kind of domain language) on XML, then why have we created XSLT
(another kind of domain language)? Can we say to the people "do not create
query languages on XML - you are not allowed to benefit from all its
advantages". Can the web ignore that sophisticated query language could be
used to fetch documents and that original URLs where created to emulate file
hierarchies and simple command lines (as found in Unix, Linux or DOS). Dont
we stretch URLs by pretending that they could be as sophisticated as some
query languages?
Conclusion: actually, any query domain language based on XML cannot be used
in the actual XML framework elements. This is the kind of limitation that me
or others had to face and this is maybe why SOAP and web services are
getting so much hype (even if SOAP also has a lot of limitations - but it
seems that the rhythm followed to resolve them is a lot faster than with the
other web technologies). Maybe the XML framework suffers now from the same
problems that SGML suffered in the past.
cheers
Didier PH Martin
[1] http://otn.oracle.com/tech/xml/content.html
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