The Bookmap specialization of ditamap supports standard book production
for collections of DITA topics. This section contains the metadata elements
used by bookmap to store book related metadata.
Note: The OASIS document type for the bookmap specialization includes the
xNAL domain specialization for describing the author or authors of a document.
All elements that appear in that domain (the authorinformation element and
all of its descendants) are described in the xNAL domain section, rather than
in this bookmap metadata section.