Since composites and element declarations do not live in the same =
`syntactic' category (in particular, the latter cannot occur directly =
under a complexType element whereas the former can), one has to make =
*some* "choice" -- be it choice or sequence. For some reason, people =
prefer the choice "sequence" rather than the choice "choice"; however =
semantically these two choices are identical as long as these =
compositors are used in their degenerated form, i.e., when there is only =
one child, as it is the case for the example at hand. In fact, there is =
a notion of "pointless" particles (composites), which however cannot be =
applied here exactly for the reason of XSD's mysterious distinction of =
expressions below complexType vs. expressions for content models in =
general ... EBNF makes my head hurt much less.

HTH,
Ralf Lammel


> -----Original Message-----
> From: xmlschema-dev-request@w... =
[mailto:xmlschema-dev-request@w...]
> On Behalf Of Florent Georges
> Sent: Wednesday, June 14, 2006 12:50 AM
> To: xmlschema-dev@w...
> Subject: xs:choice with a single choice
> 
> 
>   Hi
> 
>   I just saw the following complex type definition in the
> last XQTS (XQuery Test Suite 0.9.4) XQTSCatalog.xsd:
> 
>     <xs:complexType>
>       <xs:choice maxOccurs="unbounded">
>         <xs:element name="citation-spec" maxOccurs="unbounded">
>           <xs:complexType>
>             <xs:complexContent>
>               <xs:extension base="test:infoBase">
>                 <xs:sequence>
>                   <xs:element name="spec-URI" type="xs:anyURI"/>
>                 </xs:sequence>
>                 <xs:attribute name="name" use="required"
>                               type="test:citation-spec-enum"/>
>               </xs:extension>
>             </xs:complexContent>
>           </xs:complexType>
>         </xs:element>
>       </xs:choice>
>     </xs:complexType>
> 
>   I wonder if there is any reason to use a choice with a
> single element.  Any idea?
> 
>   Regards,
> 
> --drkm
> 
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