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--On 09 June 2002 17:08 +0700 James Clark <jjc@jclark.com> wrote:
> Certainly there is a need to be able to associate a schema with a
> document. We discussed this during the development of RELAX NG, but we
> reached the conclusion that it was better not to include this
> functionality as part of the schema language.
Another reason I forgot to mention is that I think the relationship between
instances and schemas is many-to-many. In particular, an instance can be
simultaneously valid against multiple schemas. Here I don't just mean
there may be a separate schema for each namespace: the elements in a single
namespace in a single document may be valid against multiple schemas. One
common example is that you have a both a public schema which is relatively
loose and a private schema which is much tighter. In fact, you have can
have a whole hierarchy of organizational levels (e.g. industry, company,
project), with the schema becoming less general and more specialized as you
move down the organizational tree. An approach where you specify a single
schema in the instance doesn't seem to me to deal with this scenario very
well.
James
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