unit

<xs:attribute name="unit">
  <xs:annotation>
    <xs:documentation>provides a name for the kind of unit delimited by this punctuation mark.</xs:documentation>
  </xs:annotation>
  <xs:simpleType>
    <xs:restriction base="xs:token">
      <xs:pattern value="(\p{L}|\p{N}|\p{P}|\p{S})+"/>
    </xs:restriction>
  </xs:simpleType>
</xs:attribute>