<rng:element name="refState">
 <rng:ref name="att.global.attributes"/>
 <rng:ref name="att.sourced.attributes"/>
 <rng:attribute name="unit">
  <rng:choice>
   <rng:value>page</rng:value>
   <rng:value>column</rng:value>
   <rng:value>line</rng:value>
   <rng:value>book</rng:value>
   <rng:value>poem</rng:value>
   <rng:value>canto</rng:value>
   <rng:value>stanza</rng:value>
   <rng:value>act</rng:value>
   <rng:value>scene</rng:value>
   <rng:value>section</rng:value>
   <rng:value>absent</rng:value>
   <rng:data type="Name"/>
  </rng:choice>
 </rng:attribute>
 <rng:optional>
  <rng:attribute name="length">
   <rng:ref name="data.count"/>
  </rng:attribute>
 </rng:optional>
 <rng:optional>
  <rng:attribute name="delim">
   <rng:text/>
  </rng:attribute>
 </rng:optional>
 <rng:empty/>
</rng:element>
element refState
{
   att.global.attributes,
   att.sourced.attributes,
   attribute unit
   {
      "page"
    | "column"
    | "line"
    | "book"
    | "poem"
    | "canto"
    | "stanza"
    | "act"
    | "scene"
    | "section"
    | "absent"
    | xsd:Name
   },
   attribute length { data.count }?,
   attribute delim { text }?,
   empty
}