<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="books"> <xs:complexType> <xs:sequence> <xs:element name="book" minOccurs="1" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:element name="title" type="xs:string"/> <xs:element name="author" type="xs:string"/> </xs:sequence> <xs:attribute name="is-hardback" type="xs:boolean" default="false" use="optional" /> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> </xs:schema>