30. DTD for an Attribute that Defines an External File Format

The notation attribute can be used to describe external entities and is often used to define the format of some external non XML file such as an image or audio file.

Example 30.1 An NMTOKENS Attribute Type
<?xml version="1.0" standalone="yes"?>
<!DOCTYPE rootelement [
<!ELEMENT rootelement (childelement)>
<!ELEMENT childelement (#PCDATA*)>
<!NOTATION notation1 SYSTEM "notation1value">
<!ATTLIST childelement
	sampleattributenotation NOTATION notation1 #IMPLIED>
	<childelement sampleattributenotation="notation1">
		Child element.