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RE: DTD and Schema Teasers

• To: xml-dev@l...
• Subject: RE: DTD and Schema Teasers
• From: "Bullard, Claude L (Len)" <clbullar@i...>
• Date: Wed, 17 Dec 2003 10:37:00 -0600

Thanks folks.  I much appreciate the help here.

The determinism question came up in the context of 
a wishlist being sent to the XML Schema group, so 
that is there, Michael.  By the way, congratulations 
on your recent XML Cup award.  Very appropriate and 
much deserved!

NOTE:  If I say schema, I mean Schema or DTD 
in what follows.

The multiple schemas question comes up as a *life 
among the mammals* issue for standards and specifications 
developers.  

The question originates in interpreting requirements.
If a schema is normative in a standard or specification, 
what exactly does that mean, 
or what requirements does that place on the 
developer of an implementation of the language? 
Even more befuddling for the the developer or 
user, what exactly is meant by the 'implementation', 
that is, an authoring tool, a browser, a query engine?

The pipeline answer is likely the easiest to present 
and understand.  The multiple languages answer comes 
next, but are part of the same problem when attempting 
to create a normative control.

Most don't, AFAIK, usually consider a pipeline when 
writing a specification, or if they do, they usually 
try to build a one size fits all control which I'll call  
the Gorilla Schema (Whatever the Gorilla wants, it gets).  

It can result in a control that is hard 
to relax or constrain without breaking it.  Schema 
designers have a lot of freedom and one of these is 
to mix runtime information into the language. We 
all probably understand the yins and yangs of that 
but one of them is to break the scope of the schema 
across the pipeline.

The normative schema can become this ponderous gorilla that scares 
the hairless apes or so confuses them that they immediately 
launch counter efforts to 'simplify', 'make sane', 
'reduce to...' and so on that unfortunately turn 
political.  We are likely familiar with 
this event type: the counter-spec.  This can become  
not just a technical effort, but a movement against 
the organization and individuals.  As a "His Hers And Ours" 
kid, I have an inbuilt reaction against that emotional 
response to an uncomfortable outcome of process.  

It seems to me that multiple schemas are another best practice 
issue related to the discoverable aspects of documents 
in use.   The question that one might pose is what 
relationships these emergent controls should have to the normative 
controls.  Certainly, one demands that they be compatible 
if not compliant (eg, they don't introduce productions that 
are invalid in the normative control).

The trick is to separate the emotional reaction against 
the organization from the fear of the normative control, 
and to get the organization to relax and understand that 
multiple schemas don't necessarily mean loss of control.
 
So we have an education issue.

len

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