targetNamespace - what is it for?

Could someone please explain the purpose of the targetNamespace attribute,
other than imposing restrictions on INCLUDE element?

When the value of this attribute is read and how it is used (or might be
used) by parsers and applications?
I read through 
XML Schema Part 0: Primer
http://www.w3.org/TR/2000/WD-xmlschema-0-20000407/
XML Schema Part 1: Structures
http://www.w3.org/TR/2000/CR-xmlschema-1-20001024/
Namespaces in XML http://www.w3.org/TR/REC-xml-names/
and still cannot get clear picture on that.

aa

Received on Tuesday, 3 July 2001 04:26:00 UTC