<?xml version="1.0"?> <!DOCTYPE a [ <!ELEMENT a (#PCDATA|b|s:b)*> <!ATTLIST a xmlns:s CDATA #IMPLIED> <!ELEMENT b EMPTY> <!ATTLIST b xmlns:s CDATA #IMPLIED> <!ELEMENT s:b EMPTY> <!ATTLIST s:b xmlns:s CDATA #IMPLIED> ]> <a xmlns:s="http://some.test.ns/a"> Some text. <b/> Some text. <s:b/> Some text. </a>