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   Re: [xml-dev] is xml schema bad wrt schema extensions?

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9/3/2002 4:39:45 AM, Erik Wilde <net.dret@dret.net> wrote:

> so one basic question is: 
>is this the fault of xml schema of or sloppy software authors? and, 
>regardless of that, how can this be made more safe? i think so far there 
>has been remarkably little effort to point out how to *safely and 
>reasonably use* xml schema, in contrast to the large amount of effort in 
>rather emotional schema bashing that can be seen on xml-dev...

>maybe some people will find this too complicated to be of any use, but 
>there are a lot of people out there trying to use xml schema in a 
>reasonable and robust way, and if all xml experts can come up with is 
>advice like "it's complicated and dangerous", then we do not provide 
>them a lot of help.

These are very important points.  I'd say that if the purpose of XML was
for experts to build managed systems, I would agree.  C++ is a good example of
something that is quite powerful in skilled hands but unsafe in the
hands of sloppy software authors, and the industry quite sensibly spent
a lot of effort helping people to use it in a reasonable and robust way.

To the extent that W3C XSDL is to be used by to build managed 
systems (e.g. "behind the firewall" EAI or EDI between large, established
partners), by experts who need its power, I would agree that the whining
about its complications and dangers is pointless.  But to the extent
that it is to be used on the anarchic, loosely coupled, and rapidly 
evolving Web, the whining is very much on topic, IMHO.

Pursuing the C++ analogy -- if one was building an intranet browser-based
application and wanted to give the user lots of power and ease of use,
it would make sense to use C++ to write an ActiveX control to supply
this functionality, and whining about the potential for a sloppy or 
malicious programmer would basically suggest "MANAGE your environment
better - fire the sloppy programmers or webmasters."  But if one were
deploying the application over the open Web, whining about sloppiness
and complexity suggests "start over from scratch with a more limited
but more robust system," e.g. HTML+Javascript. 

What all this suggests to me is that:

- W3C XSDL was apparently designed by ultra-power users needing 
  industrial-strength capabilities, and should be evaluated in terms
  of its suitability for that use case.  Ferraris should be evalutated
  for their ability to win races or deliver their drivers over 500 km
  of Autobahn in 2 hours, not for their ability to deliver teenagers
  to a party and back.  On the other hand, anyone handing their
  teenager the keys to the Ferrari to take his friends to the party
  richly deserves the funeral and litigation expenses that is all
  too likely to entail :-)  Ferraris *are* complicated and dangerous!
- Very few people even of the skill level of xml-dev users have yet 
  mastered W3C XSDL. Those that have tend to have either helped write it,
  or spend full-time implementing or testing it.
- More typical developers of web-based applications would be well
  advised to stick to the very basic features ("DTDs in XML syntax
  plus basic datatypes" perhaps) or to use a more novice-friendly
  alternative schema language.
- It IS critical to understand  both how experts can use W3C XSDL
  in a powerful and robust way, and how novices and use it in
  a safe and effective way, but these are two separate conversations.


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