A Plea for Schemas

[Len Bullard]

Rick Jelliffe wrote:
>
> Tim is of course correct that a schema is only part of the whole
> picture, but a schema language can be judged on how readily it allows
> useful systems and tools to be built.  

Ok.  Another way to look at it is to look at the frequency of 
change in the information and determine if a schema is an 
where in the process the schema is an effective tool.  There 
are a lot of applications whose market loosely hangs 
in the "authoring" category.  Is anyone applying schemas to dimensions 
for multi-dimensional database designs, yeVenerableHypercubes 
for online analytical processing?

> That being so, it may be a strong
> schema system is one which has some 'use' information as well as the
> "pure" schemas: documentation, forms building, validation, style, etc.:
> where the type information from the schema can directly be used for some
> purpose.
> 
> DTDs provide simple stucture models but also have infoset contributions
> with #FIXED attributes and default attribute values (i.e., a simple
> transformation of the instance). This makes them 'impure' as a schema
> language, but undoubtedly more useful.

Schemas that gracefully handle time volatility issues will be useful. 
However for that to work, the schema has to be dynamic, and I rather 
thought that was the attractiveness of XML schemas.  I can instrument 
processes and use the events to modify a schema via the DOM, thus 
closing the loop.  Better than hardwiring templates, I would think.

len



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