Based on the metadata defined in the file (attributes of the <prolog>, <topicmeta>, <bookmeta> tags), Fluid Topics generates search facets in the portal.
The language of the content is defined by the xml:lang attribute of topic and map files. If this attribute is not defined, by default the content is set to en-US.
It is possible to generate metadata for DITA content using DITA-OT plugins. For more information on how to create custom DITA-OT plugins, see Creating custom plug-ins.