<!DOCTYPE my-root [ <!ELEMENT my-root (a*)> <!ELEMENT a EMPTY> <!ATTLIST a val CDATA "nothing" fix CDATA #FIXED "constant" req CDATA #REQUIRED opt CDATA #IMPLIED> ] > <my-root> <a val="something" fix="constant" req="reading" opt="extra"/> <a req="no experience"/> <!-- OK: val = nothing, fix = constant, opt absent. --> <a fix="variable"/> <!-- Invalid! fix not constant and req unspecified. --> </my-root>