These elements qualify the topic for processes such as flagging, filtering, or retrieval.
The metadata elements apply to an entire topic, and can also be used in a map to apply metadata to multiple topics at a time. Metadata elements can expand on the values used in metadata attributes. (See metadata attributes.) For example, the audience element in a topic's prolog can define an audience in terms of type, job, and experience level, and give it a name; when there is content within the topic's body that applies only to that audience, that content can identify its audience by the same name used in the prolog.
When metadata is expressed in a map, it supplements any metadata expressed in the topics it references. When metadata in a map and a topic conflict (for example, both define a publisher), by default the value in the map takes precedence, on the assumption that the author of the map has more knowledge of the reusing context than the author of the topic.
OASIS DITA Architectural Specification v1.0 -- 09 May 2005
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