[topicmapmail] Zero or more roleplayers in XTM 1.0.1

[Marc de Graauw]

XTM 1.0.1 allows zero or more roleplayers in a member element:

  <!ELEMENT member
     ( roleSpec?, ( topicRef | resourceRef | subjectIndicatorRef )* )
  >

(Note that though the text still says "+" the DTD says "*".)

This was a change since 1.0, which required at least one. I am curious about
the reason for this change - at first sight having a member element with a
role specification but with zero role players does not seem to make sense, but
since the change was very intentional presumably there is a good reason which
I fail to see. Can anybody help? What use could this have:

<association>
  <member>
    <roleSpec>
      <topicRef xlink:href="#role"/>
    </roleSpec>
  </member>
</association>

Marc