[xml-dev] XML Schema ?

["Gregory M. Messner" <gmessner@breezefactor.com>]

I have already posted this to xmlschema-dev@w3c.org, I'm hoping someone in
this list might be able to provide an answer a little quicker.

Following is the definition of <restriction> on a simpleType (from XML
Schema Part 1: Structures):

<restriction 
  base = QName 
  id = ID 
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?, (simpleType?, (minExclusive | minInclusive |
maxExclusive | maxInclusive | totalDigits | fractionDigits | length |
minLength | maxLength | enumeration | whiteSpace | pattern)*))
</restriction>

Based on this definition, is the following XML Schema snippet valid?

<simpleType name="CryptoBinary">
  <restriction base="base64Binary"></restriction>
</simpleType>

Notice that the restriction has no content. If this is valid, then is the
intent to just extend the "base64Binary" builtin type? Or assign a different
name to the "base64Binary" builtin type? I thought <restriction> was
intended to restrict a new datatype to a *subset* of an existing type?

BTW, this type of restriction is used throughout the XML Signature Schema
Instance (xmldsig-core-schema.xsd).

Thanks,
Greg