在线引用DOCTYPE头，这样在创建文档的时候速度会比较慢。

		
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V5.0//EN"
"http://www.oasis-open.org/docbook/xml/5.0/docbook.dtd">
		
		

我们也可使使用本地的DTD文件

		
<!DOCTYPE subject SYSTEM "/usr/share/xml/docbook/schema/dtd/4.5/docbookx.dtd" [
	<!ENTITY book.info.author.xml			SYSTEM "../common/book.info.author.xml">
	<!ENTITY book.info.legalnotice.xml		SYSTEM "../common/book.info.legalnotice.xml">
	<!ENTITY book.info.abstract.xml			SYSTEM "../common/book.info.abstract.xml">
    <!ENTITY book.preface.xml           	SYSTEM "../common/book.preface.xml">
	<!ENTITY preface.about.me.xml       	SYSTEM "../common/about.me.xml">

	<!ENTITY chapter.docbook 			 	SYSTEM "chapter.docbook.xml">
	<!ENTITY chapter.docbook.doctype.xml 	SYSTEM "chapter.docbook.doctype.xml">
	<!ENTITY chapter.docbook.list.xml	 	SYSTEM "chapter.docbook.list.xml">
	<!ENTITY chapter.docbook.paragraphs.xml	SYSTEM "chapter.docbook.paragraphs.xml">
	<!ENTITY chapter.docbook.admonition.xml	SYSTEM "chapter.docbook.admonition.xml">
	<!ENTITY chapter.docbook-website.xml	SYSTEM "chapter.docbook-website.xml">
	<!ENTITY chapter.docbook.epub.xml	 	SYSTEM "chapter.docbook.epub.xml">
]>
		
		

		
<!DOCTYPE article PUBLIC "-//FreeBSD//DTD DocBook XML V4.5-Based Extension//EN" "../../../share/xml/freebsd45.dtd">