Base uri of the documents on the 'current' port

What are the base URIs of the documents that appear on the current port
in for-each and viewport?

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | It is so comic to hear oneself called
http://nwalsh.com/            | old, even at ninety I suppose.--Alice
                              | James