How to constraint occurrence of element?

Question

Hi,
I have an element while has two child elements A and B in sequence, A' occurrence can be 0 to unbound, B's occurrence can be 0 to 1, but at least one of the two elements must be occurred.
How to express such contraint in xsd?
Thanks. Robin

Answer 1

The schema is for only one of the two elements to occur. The requirement is:
but at least one of the two elements must be occurred
<?xml version="1.0" encoding="UTF-8"?><xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" attributeFormDefault="unqualified">     
<xs:element name="ROOT">     
     <xs:complexType>
<xs:choice>     
<xs:sequence>               
<xs:element name="A" maxOccurs="unbounded"/>     
<xs:element name="B"/>                              
</xs:sequence>     
<xs:sequence>                    
<xs:element name="A" minOccurs="0" maxOccurs="unbounded"/>     
<xs:element name="B"/>                                                       
</xs:sequence>     
<xs:sequence>                    
<xs:element name="A" maxOccurs="unbounded"/>     
<xs:element minOccurs="0" name="B"/>                                                       
</xs:sequence>     
</choice>     
</xs:complexType>     
</xs:element>     
</xs:schema>