<xs:complexType name="stem">
  <xs:annotation>
    <xs:documentation>Stems can be down, up, none, or double. For down and up stems, the position attributes can be used to specify stem length. The relative values specify the end of the stem relative to the program default. Default values specify an absolute end stem position. Negative values of relative-y that would flip a stem instead of shortening it are ignored.</xs:documentation>
  </xs:annotation>
  <xs:simpleContent>
    <xs:extension base="stem-value">
      <xs:attributeGroup ref="y-position"/>
      <xs:attributeGroup ref="color"/>
    </xs:extension>
  </xs:simpleContent>
</xs:complexType>