1<?xml version="1.0"?>
2<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
3 <xs:complexType name="A">
4 <xs:all>
5 <xs:element name="b" type="xs:string" minOccurs="0"/>
6 </xs:all>
7 </xs:complexType>
8
9 <xs:element name="a" type="A"/>
10</xs:schema>
11