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Joe English wrote:
> The best answer to the question "How does an XML document indicate how it
> should be processed?" is "It doesn't."
> "How does an XML document indicate how it should be processed *in system
> XYZ*?" can be answered by system XYZ.
This is a wonderfully succinct statement of the consequences of data being
autonomous from process. I would love to think that we could say 'Amen' and
leave the matter here at rest. I have, however, reluctantly concluded that
the desire for documents to express authorial intent or preference is simply
too strong and too widely held to be overcome even by repeated demonstration
of the superior usefulness of a simpler, loosely-coupled architecture.
End-to-end enforcement of the narrow intent of an original author pervades
monolithic process designs. XML gives us the opportunity for more versatile,
more reusable, and less brittle processes, but only if we understand,
respect, and enforce the difference between data and instruction.
> (XML 1.0 even defines a handy place to put such instructions -- in an
> <?XYZ ...?> PI -- but for some reason that's considered heretical.)
It is heretical, if it presumes enough a priori knowledge of process XYZ to
be comfortable instructing that process in the execution of its own