The format attribute

The following values for format have special processing implications:

dita

The destination uses DITA topic markup or markup specialized from a DITA topic. Unless otherwise specified, when format is set to "dita", the value for the type attribute will be treated as "topic".

ditamap

The linked-to resource is a DITA map. It represents the referenced hierarchy at the current point in the referencing map. References to other maps can occur at any point in a map, but because relationship tables are only valid as children of a map, referenced relationship tables are treated as children of the referencing map.

Note: If a topicref element that references a map contains child topicref elements, the processing behavior regarding the child topicref elements is undefined.

(no value)

The processing default is used. The processing default for the format attribute is determined by inspecting the value of the href attribute. If the href attribute specifies a file extension, the processing default for the format attribute is that extension, after conversion to lower-case and with no leading period. The only exception to this is if the extension is "xml", in which case the default format is "dita". If there is no extension, but the href value is an absolute URI whose scheme is "http" or "https", then the processing default is "html". In all other cases where no extension is available, the processing default is "dita".

If the actual format of the referenced content differs from the effective value of the format attribute, and a processor is capable of identifying such cases, it MAY recover gracefully and treat the content as its actual format, but SHOULD also issue a message.