Mapgroup domain elements
The mapgroup domain elements define, group, or reference content. Many of the mapgroup elements are convenience elements; they simply provide shortcuts for an author to use existing markup.
For example, the <topichead> element
enables a map to specify a heading without a reference to a topic.
While a <topicref> element might accomplish
the same thing by creating a title and leaving off the
@href attribute, the
<topichead> element makes the intent
clearer and prevents the accidental inclusion of an
@href attribute.