The DocBook DTD

Most XSLT processors also validate the XML, so you need access to the DocBook XML DTD

Standard header to a DocBook XML file is:

<?xml version="1.0"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">

If used, most XSLT processors require you to be online

	Tip
	xsltproc supports the use of XML Catalogs which map identifiers to locally installed DTDs

If you are not online and do not have XML Catalog support, you need to change header to path where DTD is installed

<?xml version="1.0"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
"/usr/share/sgml/docbook/xml-dtd-4.1.2/docbookx.dtd">