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RE: XML Schemas: Best Practices
- From: "Bullard, Claude L (Len)" <email@example.com>
- To: "Roger L. Costello" <firstname.lastname@example.org>, email@example.com
- Date: Fri, 05 Jan 2001 14:32:29 -0600
After twisting this a few times (like a
Rubik's Cube), my opinion. If indeed you want the
choices to come from separately developed
sources, you are as you say probably down to the
choice, aka, Or group, aka, Switch. Otherwise,
assume a separate non-Schema, say human readable
(aggggghghgh!) control exists.
Why? The other two by definition involve
a structural and by inference, perhaps,
semantic commonality which to exist
must have some common control/rule/contract
to constrain them. In other words,
you have defined a chicken or egg problem
that has no solution until you
1. Decide that there is a structural relationship
and a type relationship, meaning, you
have prior knowledge, or
2. Decide that this is a choice among black boxes
with all private information, therefore, you
need no prior knowledge; just that all
choices are equally probable and the only
semantic is "containment".
For the constraints of your ideal, you have
to know what you mean by "disjoint" or
"independent" development. Just as
systems like COM need a common and
enforced contract for discovery of the
interfaces (e.g., must implement IUnknown),
you preclude this contract with "independent"
and "disjoint" development. Therefore,
content which is perfectly substitutable
requires the container and by implication
the processing semantic to also "not care".
The Choice is the laissez-faire or "only
local implementation knows" or "or results
unspecified or see Documentation" practice.
The rest have a semantic of type. These
are a separate Best Practice question.
Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h