Extension of xs:anyType

I've been looking at the HL7 schema and I see that a type is defined to be 
an extension of an xs:anyType, as shown below...

 <xsd:complexType name="varies">
  <xsd:complexContent>
   <xsd:extension base="xsd:anyType"/>
  </xsd:complexContent>
 </xsd:complexType>

This type is then used in the following situation...

  <xsd:complexType name="MFA.5.CONTENT">
    <xsd:complexContent>
      <xsd:extension base="varies">
        <xsd:attributeGroup ref="MFA.5.ATTRIBUTES"/>
      </xsd:extension>
    </xsd:complexContent>
  </xsd:complexType>

What sorts of XML instances does this map to?  Also, what would you expect 
(in an ideal world!) a data binding tool to do in this context?

I notice that the uses only add attributes.  Could the construct also have 
elements added to it?

Is there a section of the spec I should look at to describe this?

Thanks for any explanations.  (Apologies if this is an FAQ!)

Pete.
--
=============================================
Pete Cordell
Tech-Know-Ware Ltd
                         for XML to C++ data binding visit
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                         (or http://www.xml2cpp.com)
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