The branch filtering mechanism enables map authors to set filtering conditions for specific branches of a map. This makes it possible for multiple conditional-processing profiles to be applied within a single publication.
Without the branch filtering mechanism, the conditions specified in a DITAVAL document are applied globally. With branch filtering, the ditavalref element specifies a DITAVAL document that can be applied to a subset of content; the location of the ditavalref element determines the content to which filtering conditions are applied. The filtering conditions then are used to filter the map branch itself (map elements used to create the branch), as well as the local maps or topics that are referenced by that branch.
The ditavalref element also provides the ability to process a single branch of content multiple times, applying unique conditions to each instance of the branch.