Pull content into topics (topicpull)
  
  
  The topicpull step pulls content into <xref> and
      <link> elements. This step is implemented in XSLT.
If an <xref> element does not contain link text, the target is examined and the link
        text is pulled. For example, a reference to a topic pulls the title of the topic; a reference to a list item
        pulls the number of the item. If the <xref> element references a topic that has a short
        description, and the <xref> element does not already contain a child
          <desc> element, a <desc> element is created that contains the
        text from the topic short description.
The process is similar for <link> elements. If the <link> element
        does not have a child <linktext> element, one is created with the appropriate link text.
        Similarly, if the <link> element does not have a child <desc>
        element, and the short description of the target can be determined, a <desc> element is
        created that contains the text from the topic short description.