<preface>The <preface> element references a topic or map containing
introductory information about a book, such as the purpose and structure of the document.
See appendix for information about this element in OASIS document type shells.
- map/topicref bookmap/preface
See the example in bookmap.
The following attributes are available on this element: Universal attribute group, Link relationship attribute group (with a narrowed definition of @href,
given below), Attributes common to many map elements, @navtitle and @copy-to
from Topicref element attributes group, outputclass, and @keyref.
@href<topicref>. See The href attribute for detailed information on supported values
and processing implications. References to DITA
content cannot be below the topic level: that is,
you cannot reference individual elements inside a
topic. References to content other than DITA
topics should use the @format
attribute to identify the kind of resource being
referenced.