Types of Attributes (4)

• ID
• Unique Identifier of the attribute.
• A particular value should not appear more than once in an XML document.
• The first character must be a character, '_', or ':'
• The following characters may not include whitespaces.

     <!ELEMENT student_name (#PCDATA)>
     <!ATTLIST student_name student_id ID #REQUIRED>
	    
     <student_name student_id="S9216735">Jo Smith</student_name>