xml-dev - Re: Various presentations, schema concepts, etc.

[Rick JELLIFFE <ricko@geotempo.com>]

KenNorth wrote:

> That development paradigm was procedural and process-oriented. The industry
> has since moved to object-orientation, and I think we're about to make the
> next great leap -- declarative programming. We'll express rules and
> constraints instead of designing processes or objects.

But underneath that may still be a certain tension between XML as
espoused by vendors with different schema-compilation strategies:

 1) static, public  -- e.g. closed schemas in public repositories, or
purely local to the document

 2) static, extensible -- e.g. open schema with clear positions in which
      extensions can be declared; public base types customized (extended
or     
     restricted or overlapped) as required; but all type info declared
in
     the schema itself.

 3) dynamic, extensible -- e.g. where the instance itself may contain 
   constraints and declarations (such as <table cols='4'>... where the 
   number of columns will be 4).

I think XML Schemas represents the shift from 1) to 2)  but its
(correct) emphasis on providing an acceptable fit with RDBMS and Object
systems means that supporting stage 3) schemas will be the subsequent
great leap forward, not the one impending from XML Schemas.  

As a side-issue, I predict that XML Schemas will help us understand what
people do with DTDs much better too: that will in turn feed into future
Schema extensions or overlays or enhancements.


Rick Jelliffe

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