<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="a" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="a">
    <xs:complexType mixed="true">
      <xs:sequence>
        <xs:element ref="b:b" maxOccurs="unbounded" minOccurs="0" xmlns:b="b"/>
        <xs:element ref="notb:b" xmlns:notb="notB"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>