Re: inquiry into the <choice> element behavior

Original Message From: Jeffrey.Kramer

> We were hoping to get a definitive answer on how the <choice> element is
> supposed to behave.
>
> We observed kind of a counter intuitive result of choice in a test.  i.e.,
> we'd think it was going to be mutually exclusive across it's elements,
> although when we provided >1 types it actually spit out both ( see below )

The result you are getting for the XSD segment you show is correct.  You've 
effectively allowing multiple instances of the choice, where each choice is 
independent, much as if you had:

    ChoiceClass[]  myChoices;

If you wanted one option or the other, but wanted to allow multiple 
instances of which ever one was chosen, you would do something like the 
following XSD segment:

   <xs:choice>
      <xs:element name="foo" type="xs:string" maxOccurs="unbounded"/>
      <xs:element name="bar" type="xs:string" maxOccurs="unbounded"/>
    </xs:choice>

HTH,

Pete Cordell
Codalogic Ltd
Interface XML to C++ the easy way using XML C++
data binding to convert XSD schemas to C++ classes.
Visit http://www.codalogic.com/lmx/ for more info

----- Original Message ----- 
From: <Jeffrey.Kramer@dds.net>
To: <xmlschema-dev@w3.org>
Sent: Thursday, October 30, 2008 6:45 PM
Subject: inquiry into the <choice> element behavior


> We were hoping to get a definitive answer on how the <choice> element is
> supposed to behave.
>
> We observed kind of a counter intuitive result of choice in a test.  i.e.,
> we'd think it was going to be mutually exclusive across it's elements,
> although when we provided >1 types it actually spit out both ( see below )
>
> i.e.,
>
> providing
> ....
>        <foo>1</foo>
>        <foo>2</foo>
>        <bar>3</bar>
> ...
> to
> ..
>         <xs:choice  maxOccurs="unbounded">
>            <xs:element name="foo" type="xs:string" />
>            <xs:element name="bar" type="xs:string" />
>       </xs:choice>
>
> yields:
>
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #startElement:
> foo
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #characters: 1
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #endElement: foo
>
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #startElement:
> foo
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #characters: 2
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #endElement: foo
>
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #startElement:
> bar
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #characters: 3
> 2008-10-30 11:55:17,726 main DEBUG xml.UnmarshalHandler - #endElement: bar
>
>
> We were kind of thinking the choice would somehow be limited to only one
> of nested elements.  Perhaps we're misusing the maxOccurs?   Any insights
> greatly appreciated.  Thanks in advance.
>
> - Jeff
>
>
>