To reduce the number of variants of essentially the same hierarchy, when you define an element path (see §6.4.1 Understanding element paths), you might want to treat several elements as equivalents; for example, topic, concept, task, and reference. You can define a single element set that includes them all, and reference that element set in the element path.
[ElementSets]
; Name for set = list of elements and element sets, separated by
; spaces.
$setname = element1 element2 $otherset
Give each set an alphanumeric name prefixed with a $ (dollar sign). List the names of members of the set to the right of the equals sign, separated by spaces. For example:
[ElementSets]
$topic = topic concept task reference glossentry
$body = body conbody taskbody refbody glossdef
$sect = section example refsyn
$map = map bookmap
$tref = topicref topichead chapter frontmatter backmatter
A member of an element set can be either of the following:
Member sets must be defined in [ElementSets] above any other sets that include them. Keep the definition of each set all on one line in your configuration file.