"jeroen bekaert" <jbekaert@l...> writes:

> Derivation by extension can be used to append new content after the
> content of the base type; however - if not mistaken - the structure of the
> base type must be kept unchanged. As such, it is not possible to derive a
> mixed content model from an element-only content model (and vice versa).

Correct.

> The content type of the base type definition of SCHEMA 1 below is empty.
> Is it correct to derive (by extension) a content type 'mixed' of a base
> type definition with an empty content type?

Yes.

> Can someone point me to the clause of the W3C XML Schema spec
> confirming/forbidding the below extension constructs?

>From Schema Component Constraint: Derivation Valid (Extension) [1]

  1.4.3 All of the following must be true:
    1.4.3.1 The {content type} of the complex type definition itself
            must specify a particle.
    1.4.3.2 One of the following must be true:
      1.4.3.2.1 The {content type} of the {base type definition} must
                be _empty_.
      1.4.3.2.2 All of the following must be true:
        1.4.3.2.2.1 Both {content type}s must be _mixed_ or both must be
                    _element-only_.
        . . .

Hope this helps,

ht

[1] http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/structures.html#cos-ct-extends
-- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
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From K.Buchcik@4... Wed Mar 16 10:14:05 2005
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