[OFFTOPIC] Re: [XML-SIG] XML-SCHEMA

[Ken MacLeod]

Christian Tismer <tismer@trixie.triqs.com> writes:

> Ken MacLeod wrote:
> > 
> > Christian Tismer <tismer@tismer.com> writes:
> [a little about Schemas]
> ...
> > I respect the functionality of XML Schema, but to claim its XML
> > grammar as "more powerful and easy to read" is a big reach.
> 
> Sorry, it is more powerful than a DTD and easier to read.
> Feel free to prove the opposite. I'm prepared well.

I think you may have misinterpreted my comment.  My comment was
specifically in reference to "But it's all XML, no DTD needed".  I
took this statement to mean "it's better because it's in XML syntax,
instead of being in a schema specific syntax".  I wasn't trying to say
DTDs were better than XML Schema, but that XML Schema itself would
likely be "more powerful and easy to read" if it had it's _own_ syntax
rather than layering over XML.

You later wrote:
> Writing a schema processor would not involve to write a new XML
> parser per se, but you would use an existing, probably
> non-validating parser, maybe one that validates the XSD file.

Which, although true, does not make the syntax necessarily more
powerful or easier to read for the most important part of the
equation: the user who has to write it.  In other words, XMLAuthority
wouldn't be a required necessity if the syntax of the language (XML
Schema) weren't so convoluted because it's _in_ XML.

A parallel is the thread here a few months back about expressing
programming languages in XML.  Sure, it's possible, but would _you_
want to write a program in XML rather than Python?  I wouldn't.

> > That ranks up there with using a DOM interface to your application's
> > data as one of the biggest misuses of XML.
> 
> What do you try to express by this?

A common mistake in using XML, similar in spirit to XML Schema being
expressed in XML, is for people to access their application data
through a layer of XML exposed through DOM.  DOM is an interface to
XML information.  Accessing application data represented via XML
information is an unnecessary and burdensome layer; far better to
simply convert the XML into application objects and use those
directly.

  -- Ken