[xml] How to use a schemas without targetNamespace in catalog?

[Liu Xuewu <lxw wingold cn>]

Hi,sir,

  Is there some way to use a schemas without targetNamespace in catalog?
  For example, for a xml schema without targetNamespace as follow:

  <?xmlversion="1.0" encoding="utf-8"?>
  <schema xmlns="http://www.w3.org/2001/XMLSchema";
elementFormDefault="qualified">
    <element name="someelement">
     ........
    </element>
  </schema>

  and in an xml instance document:

  <?xmlversion="1.0" encoding="utf-8"?>
  <someelement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xsi:noNamespaceLocation="someUri">
      ......
  </someelement>

  Now I wonder how to add the schema in catalog.