Re: optional, but at least one required

That's a pretty straightforward solution. I look forward to using it 
:)

Regarding the previous message, Michael, where does one draw the line 
at including every rule in the schema? Some things are more easily 
done when processing, for sure. But it's good to know that I can't get 
arrested for leaving something out of the schema :)

On Thu, 11 Oct 2007 14:38:13 +0100
  "Michael Kay" <mike@saxonica.com> wrote:
> 
>> XSD1.1 is looking at adding an xs:assert schema directive 
>> that includes a set of xpath expressions that a construct 
>> (sequence/choice/etc.) must satisfy.  I would be interested 
>> to know how complicated such an expression for this use-case 
>> would be if anyone cared to submit an example.
> 
> You can write it as
> 
>  <xs:sequence>
>    <xs:element ref="a" minOccurs="0"/>
>    <xs:element ref="b" minOccurs="0"/>
>  </xs:sequence>
>  <xs:assert test="a|b"/>
> 
> Michael Kay
> http://www.saxonica.com/
> 
> 
>