new to xml

[admin]

can anyone give me a brief of what and how to use it.this is what i've written.<?xml version="1.0" encoding="iso-8859-1"?><!ELEMENT DOCUMENT(AUTHOR+)><!ELEMENT AUTHOR(author_id,author_lname,author_fname,phone,address,city,state,zip,contract)><!ELEMENT author_id(CDATA)><!ELEMENT author_lname(CDATA)><!ELEMENT author_fname(CDATA)><!ELEMENT phone(CDATA)><!ELEMENT address(CDATA)><!ELEMENT city(CDATA)><!ELEMENT state(CDATA)><!ELEMENT zip(CDATA)><!ELEMENT contract(CDATA)></xml>can u tell me anything is wrong with this