Susan Harris wrote:
> I have a document that includes info similar to:
> 
> <cat>
>  <name>Tiddles</name>
>  <color>Purple</color>
>  <age>12</age>
>  <ageInCatYears>84</ageInCatYears>
> </cat>
> 
> ALL elements (including <cat>) are optional. However, <cat> should not 
> exist unless at least one of it children does.
> 
> How can I specific via an XML schema that <cat> should not exist unless 
> it has at least one child?


   <xs:element name="cat">
     <xs:complexType>
       <xs:choice maxOccurs="unbounded">
         <xs:element name="name" type="xs:string"/>
         <xs:element name="color" type="xs:string"/>
         <xs:element name="age" type="xs:int"/>
         <xs:element name="ageInCatYears" type="xs:int"/>
       </xs:choice>
     </xs:complexType>
   </xs:element>

would suffice to ensure that the 'cat' element has at least one of the 
child elements listed in the choice. On the other hand the above 
definition would allow several 'name' or 'color' or 'age' elements so I 
doubt you want that construct.

So whether there is a solution depends on the other constraints you want 
to put on the children of 'cat'.

-- 

	Martin Honnen
	http://JavaScript.FAQTs.com/