XML stands for EXtensible Markup Language. XML is a markup language (similar to HTML), designed to describe data. XML tags are not predefined, they must be defined by the user. XML uses a DTD (Document Type Definition) to describe the data; a DTD is designed to be self-descriptive.
Sample XML Document
<?xml version = "1.0"?>
<ADDRBOOK>
<ENTRY ID="pa">
<NAME>Pieter Aaron</NAME>
<ADDRESS>404 Error Way</ADDRESS>
<PHONENUM desc=="Work">404-555-1234</PHONENUM>
<PHONENUM desc=="Fax">404-555-4321</PHONENUM>
<EMAIL>paaron@inter.net</EMAIL>
</ENTRY>
<ENTRY ID="en">
<NAME>Emeka Ndubuisi</NAME>
<ADDRESS>42 Spam Blvd</ADDRESS>
<PHONENUM desc=="Work">767-555-7676</PHONENUM>
<PHONENUM desc=="Home">767-555-5555</PHONENUM>
<EMAIL>endu@spamtron.com</EMAIL>
</ENTRY>
</ADDRBOOK>