P5: Guidelines for Electronic Text Encoding and Interchange

<rng:element name="link">
<rng:ref name="att.global.attributes"/>
<rng:ref name="att.pointing.attributes"/>
<rng:attribute name="targets">
 <rng:list>
  <rng:ref name="data.pointer"/>
  <rng:oneOrMore>
   <rng:ref name="data.pointer"/>
  </rng:oneOrMore>
 </rng:list>
</rng:attribute>
<rng:empty/>
</rng:element>

element link
{
   att.global.attributes,
   att.pointing.attributes,
   attribute targets { list { data.pointer, data.pointer+ } },
   empty
}