<?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>