The metadata elements, many of which map to Dublin core metadata, are available in topics and DITA maps. This design enables authors and information architects to use identical metadata markup in both topics and maps.
The <metadata> element is a wrapper element that contains many of the
metadata elements. In topics, the <metadata> element is available in the
<prolog> element. In maps, the <metadata> element
is available in the <topicmeta> element.
In DITA maps, the metadata elements also are available directly in the
<topicmeta> element. Collections of metadata can be shared between DITA
maps and topics by using the conref or keyref mechanism.
In general, specifying metadata in a <topicmeta> element is equivalent
to specifying it in the <prolog> element of a referenced topic. The value
of specifying the metadata at the map level is that the topic then can be reused in other maps
where different metadata might apply. Many items in the <topicmeta>
element also cascade to nested <topicref> elements within the map.
<metadata> element.
However, they are available in either the topic <prolog> element or the
map <topicmeta> element.