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   RE: [xml-dev] Fallacies of Validation ... RE: [xml-dev] Are people reall

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From: Roger L. Costello [mailto:costello@mitre.org]

>Yesterday Len Bullard made a similar statement:

>> ... most fundamental errors are ... to consider only a single schema.

Even if one thinks it easier to manage a single schema, command and 
control in adaptive systems is distributed.  A schema is a control. 
Sometimes it is useful to have one control: think old TVs with 
volume and channel selectors.  Sometimes, to be flexible with 
respect to a variant environment, it is better to have multiple 
controls.  Think of component stereos with equalizers, filters, 
etc.  Rick J. nailed it: variant and invariant conditions.  Just 
remember, this describes not only the system, but the hosting 
environment as well.  A self-directed evolving system monitors 
changes in the environment and adapts to them.  This is also 
known as event-based notification.

> ... fall into the trap of thinking of THE schema and not 
> recognizing the system as a declarative ecosystem of schemas 
> and schema components.

Not should, but can be and often is.  If these are isolates, it 
doesn't matter much how singular or multiple they are; but when 
they are in an ecosystem, they typically overlap and exchange 
information, and adapt as a result.  That is why the emphasis 
is on ecotonal relationships, eg., where tundra meets forest 
what species do we find.

>It would be very useful if we could have a simple example that shows how
>several schemas might be employed, rather than a single schema.  Could
>someone provide an example?  

Look at any large reporting system.  You can build that up a large schema 
but given local variations, do you have sufficient power/force/authority 
to make them stick or will you be constantly adjusting them, loosening 
them, strengthening them, and how will you know which is the right 
thing to so?  It is of little use to be aware of context unless you 
have some means to determine what is important in the context relative 
to the goals of the transaction.   The example of the Draconian parse 
rule is a good one:  in what situations should it be relaxed?

>Len, I like the term you used, "declarative ecosystem".  Could you
>upon what this means?


It means declarative definitions that overlap in a dynamic messaging
It can be random and exhibit behaviors like Brownian motion, or aware and
directed, or simply patterned.  The essence of intelligence is not
but self-directed adaptation.  An intelligent system learns.  It not only
memory, it has a goal seeking behavior that can use memory to more
select behaviors.  It is not trapped in the past.  It speaks the future into


> ... most fundamental errors are to consider schemas only at the external
> system junctions ...

The problem of locale is that it is declared locally but might require 
global management.  Think of the British mail system vs the American 
mail system.  The American system is far more efficient.  The British 
system is more colorful.  It is easier to send mail in the US.  Size 
matters.  The Brits can use a system such as MI5; the Americans can't. 

The problem is the numbers of active interfaces being routed to one 
or a few receivers.  Sometimes, a single schema suffices for the whole 
system.  Sometimes, you needs lots of little ones.  The reasons may be 
scale or legacy (the way in which it grew and the decisions made for 
local reasons forced to the top as global policy).  The reality is that 
social decisions matter.  We engineer to these until the system decides 
it can't afford that any longer.  Then we see standards with teeth or 
small groups breaking off and creating keiretsu:  think Intel + Adobe, 
or Sony + whoever.  Should I use ArcXML because ESRI dominates the 
market and supports proprietary dialects, or should I work hard to 
get ESRI to support GML because my customer demands open standards? 
Should I slow the system down with XSLT?  Should I use IE because 
MS won the desktop hegemony?

I can't separate social rules from engineering fundamentals. I 
apply engineering fundamentals to implement social rules.

No size fits all.



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