XML Example - the DTD
Create a DTD file for an address book named “ab.dtd”
<!ELEMENT addressBook (person)+>
<!ELEMENT person (name, email*, link?) >
<!ATTLIST person id ID #REQUIRED >
<!ATTLIST person gender (male|female)#IMPLIED >
<!ELEMENT name (#PCDATA|(family,given))>
<!ELEMENT family (#PCDATA)>
<!ELEMENT given (#PCDATA)>
<!ELEMENT email (#PCDATA)>
<!ELEMENT link EMPTY > <!ATTLIST link manager IDREF #IMPLIED subordinates IDREFS #IMPLIED >