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In my mind, choosing one schema over another is driven by the depth of
validation I can express and execute with each. Can I validate with a
regular expression? Can I express cross-field constraints? Is there a
mini-language to do arbitrary computational tests? Can external
validation and consistancy, including relational-style tuple existance
be expressed in an abstract way?
When we have actually used Schemas, these are the kinds of things that
became apparent needs. It may be that some particular line delineates
what should and should not be in a schema, but it is apparent that this
will evolve. First is syntax and minor semantics, full semantic
validation seems a logical path, but implies a lot potentially. There
are multiple solutions, probably explored by committees in the past.
"Baby steps. Baby steps. When you're ready."
Now, is it additionally important to efficient load (somewhat) and
'execute' (definitely) a schema? Does it need to have a binary
Schemas can usually be cached, precomputed, and involve other
efficiencies. You can think of situations where this doesn't hold.
Still, it's nothing like the efficiency needs of the data itself.
Bullard, Claude L (Len) wrote:
>I don't buy it. I buy that people are creating alternative
>syntaxes, alternative applications (eg, RELAX NG which may
>or may not have an 'unstoppable momentum' but has yet to
>show up in an RFP so not in prime time yet). I don't buy
>that these are easier to learn or read once one is comfortable
>with XML. To me the ease of any one feature or the complexity of
>any one language is quickly overcome by the network effect of
>instances and tools shared widely.
>Is a binary characterization group a mandate to open up a
>full up replacement or large scale revision of XML? I doubt
>it. Syntax is NOT trivial.
>We've had simpler syntaxes before. We've had binaries before.
>We've never had integration at this scale. We have to be very
>conservative what of the various experiments in the wild are
>adopted into the standards of a working system.
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