side

<xs:attribute name="side" default="right">
  <xs:simpleType>
    <xs:restriction base="xs:string">
      <xs:enumeration value="left"/>
      <xs:enumeration value="right"/>
      <xs:enumeration value="leftoverlap"/>
      <xs:enumeration value="rightoverlap"/>
    </xs:restriction>
  </xs:simpleType>
</xs:attribute>