L.S.,
From another forum I got a response. They suggested filling in the action-field with the namespace of the site (which I did) and filling in the "to-field", both of them in the WS-A tab. After filling in these two field I got rid of the error. Nevertheless, thanx for putting me on the right track.
It appears difficult, in general, to find more basic requirements with regard to field-values for using SOAP (not considering the official oasis-open documents, which are quite unreadable ;-)). I also found some usable information on the
http://aws.amazon.com sincerely
IP