<preface>
The <preface> element references a topic or map containing
introductory information about a book, such as the purpose and structure of the document.
Specialization hierarchy
The <preface> element is specialized from
<topicref>. It is defined in the bookmap module.
Attributes
The following attributes are available on this element:
common map attributes, link-relationship attributes, universal
attributes,
and @keyref.
Example
See the example in bookmap.