[relax-ng] ns attribute

I noticed in the RELAX NG Schema for RELAX NG that the ns attribute is
declared:

<define name="common-atts">
 <optional>
  <attribute name="ns"/>
 </optional>
 ...

Shouldn't it have a type of anyURI? Like this:

<define name="common-atts">
 <optional>
  <attribute name="ns">
   <data type="anyURI"/>
  </attribute>
 </optional>
 ...

Mike