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Re: HL7 use of xs:anyType extension

• To: xml-dev@l...
• Subject: Re: HL7 use of xs:anyType extension
• From: Boris Kolpackov <boris@c...>
• Date: Thu, 8 Jun 2006 07:10:56 +0000 (UTC)
• References: <006c01c6896e$e8e7a1a0$0600a8c0@RW>
• Sender: news <news@s...>
• User-agent: nn/6.6.5+RFC1522

Hi Pete,

"Pete Cordell" <petexmldev@t...> writes:

>  <xsd:complexType name="varies">
>   <xsd:complexContent>
>    <xsd:extension base="xsd:anyType"/>
>   </xsd:complexContent>
>  </xsd:complexType>
>
> I've seen (incorrect) comments on the web that say this is an attempt to
> define an empty element.  Is this HL7's intent?  Or is it just an attempt to
> map the name 'varies' to xsd:anyType?

I believe varies is just an alias for anyType.


> The above 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 should this map to?  An empty element with
> attributes as defined in the attributeGroup?  Or, any number of attributes
> and element body content, that must also include the set of attributes
> defined in the attributeGroup?  i.e. is this some way of defining an
> extensible instance?

I think this definition does not make any sense. anyType matches any
content. If we agree that, in case of an extension, a base type is
matched before derived (which appears to be the case from the spec)
then base anyType will match everything and not leave anything to the
extension.

So I would say that if MFA.5.ATTRIBUTES defines any required attributes,
then the set of valid contents for this type is empty. Otherwise any
content matches with attributes from MFA.5.ATTRIBUTES never getting any
value.

hth,
-boris


-- 
Boris Kolpackov
Code Synthesis Tools CC
http://www.codesynthesis.com
Open-Source, Cross-Platform C++ XML Data Binding

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