DocBook is a DTD - Document Type Definition. now what is this? well
say for example having said XML is in itself a rule set , suppose i use an
markup element tag <author> in my document and another author uses <writer> element
tag in his document, isn't it true we are trying to convey the same meaning .Imagine thousands of
pages are being written for the web, for the publishing industry and what a waste of enormous
time if people would like to convey similar meaning but use different elements with the core
language being same, this is where an DTD comes into picture.
Docbook DTD is a very popular set of tags for describing books,
articles and other prose documents, particularly technical documentation. Docbook
is defined using the native DTD syntax of SGML
and XML. Like HTML, DocBook is an example of
a markup language defined in SGML/XML.
|---From the book DocBook -
The Definitive Guide by Norman Walsh and Leonard Muellner.