<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:group name="name">
    <xs:choice>
      <xs:element name="name" type="xs:string"/>
      <xs:sequence>
        <xs:element name="first-name" type="xs:string"/>
        <xs:element name="middle-name" type="xs:string" minOccurs="0"/>
        <xs:element name="last-name" type="xs:string"/>
      </xs:sequence>
    </xs:choice>
  </xs:group>
  <xs:element name="author">
    <xs:complexType>
      <xs:group ref="name"/>
    </xs:complexType>
  </xs:element>
</xs:schema>