|DITA map files / DITA map vocabulary|
The basic building block of ditamap files is the topic reference (topicref) element.
Topic references nominate the topic or other resource to be included in the collection. They are similar in function to a cross-reference (xref) element in topic content.
The topicref element is used for the hierarchical section of the ditamap and the relationship table section.
Resources that a topicref element can reference include DITA topics within the collection, (embedded) ditamaps, DITA topics external to the collection, external files, and Internet resources.
The main attributes of the topicref element are the href, scope, format, and type attributes.