<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="unqualified">

    <xs:attribute name="Attribute">
        <xs:simpleType>
            <xs:restriction base="xs:NMTOKEN">
                <xs:enumeration value="foo" />
                <xs:enumeration value="bar" />
                <xs:enumeration value="baz" />
            </xs:restriction>
        </xs:simpleType>
    </xs:attribute>

    <xs:element name="Element">
        <xs:complexType>
            <xs:attribute ref="Attribute" use="required" />
        </xs:complexType>
    </xs:element>

</xs:schema>
