Example: Single <ditavalref> in a reference to a map
In the following example, other.ditamap is referenced by a root map.
               The <ditavalref> element indicates that all of the content in
               other.ditamap should be filtered using the conditions specified in
               the some.ditaval document.
            
Map fragment
<topicref href="parent.dita">
  <topicref href="other.ditamap" format="ditamap">
    <ditavalref href="some.ditaval"/>
  </topicref>
</topicref>Contents of other.ditamap
<map>
  <topicref href="nestedTopic1.dita">
    <topicref href="nestedTopic2.dita"/>
  </topicref>
  <topicref href="nestedTopic3.dita"/>
</map>This markup is functionally equivalent to applying the conditions in
               some.ditaval to the topics that are referenced in the nested map. For
               the purposes of filtering, it could be rewritten in the following way. The extra
               <topicgroup> container is used here to ensure filtering is not
               applied to parent.dita, as it would not be in the original
               example:
<topicref href="parent.dita">
  <topicgroup>
    <ditavalref href="some.ditaval"/>
    <topicref href="nestedTopic1.dita">
      <topicref href="nestedTopic2.dita"/>
    </topicref>
    <topicref href="nestedTopic3.dita"/>
  </topicgroup>
</topicref>
            
            For the purposes of filtering, this map also could be rewritten as follows.
<topicref href="parent.dita">
  <topicref href="nestedTopic1.dita">
    <ditavalref href="some.ditaval"/>
    <topicref href="nestedTopic2.dita"/>
  </topicref>
  <topicref href="nestedTopic3.dita">
    <ditavalref href="some.ditaval"/>
  </topicref>
</topicref>
            Filtering based on the <ditavalref> element
               applies to the containing element and its children, so in each case, the files
               nestedTopic1.dita, nestedTopic2.dita, and
               nestedTopic3.dita are filtered against the conditions specified in
               some.ditaval. In each version, parent.dita is
               not a parent for the <ditavalref>, so it is not filtered.