[no subject]

ownerElement of type Element, readonly 
  The Element on which the namespace was in scope when it was requested.
  This does not change on a returned namespace node even if the document
  changes such that the namespace goes out of scope on that element and this
  node is no longer found there by XPath.

we would also get the ownerDocument attribute from this.

2. For proper memory management with namespace nodes.  We need to know the 
document that contains the namespace so we know when we can delete a
document tree.  If we had ownerElement, then we could find the owner
document.

Thanks,
TJ