xslt - find all elements with unknown namespace

i have a very generic xml schema allowing any additional data - and i want to process that data with xslt. the xsd part looks like that:

<xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded">
 <xs:annotation>
  <xs:documentation>any additional properties</xs:documentation>
 </xs:annotation>
</xs:any>

now i want to process that information with xslt. i thought of something like: "find every element that has an unknown namespace." is sthg like that possible? our do you have a better suggestion on how to proceed?

BR