<element
name='field'>
<complexType>
<attribute name='tag' use='fixed' value='20'/>
</complexType>
</element>
</sequence>
</restriction>
</<complexContent>
</complexType>
...
> > The definition of restriction in XML Schema reads:
>
>
> > >A type definition whose declarations or facets are in
a
> > >one-to-one relation with those of another specified
type
> > >definition, with each in turn restricting the
possibilities
> > >of the one it corresponds to, is said to be a
restriction.
>
>Note this is an introductory summary early in the
spec.
This is actually Definition 2 in 2.2.1.1. Looks like the official
definition of restriction, unless someone can point to a "more"
official definition. According to this definition, my derivation
'myfields' is in error! I have to rewrite 'fields' as:
<complexType name='fields'>
<sequence>
<element name='field'>
<complexType>
<attribute
name='tag'/>
</complexType>
</element>
<element name='field'>
<complexType>
<attribute
name='tag'/>
</complexType>
</element>
</sequence>
</complexType>
Of course, an elegant semantic definition we all prefer can be
( actually in "an introductory summary early in the spec"):
"...the values represented by the new type are a subset of the values
represented by the base type ..."
But this definition is not computationally feasible! It got to
be
NP-hard to compare the language sets defined by two schemas.
I am glad that you brought up the issue of Unique Particle
Attribution constraint. It is also a computational feasibility
challenge to enforce. Finding that one instance element looks
NP-Complete to me again.
I expect syntax-oriented, but more elaborate definitions
dictated by standards. Where is it? Did I lose a page in my book? :-)
Jay Zhang
IntermicsTech, Inc.
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