Hi David
Thanks for your answer.. Since it's a completely new application (not a replacement or refactoring of an existing application), i decided to do it in XPages.. the customer works mainly in the notes client, sometimes over the web client, and with planning to take use of Social Experienca (typical workflow application).. If they have the Notes Client available, the don't want to leave it (understandable)..
If the window handling would become a serious problem, i might have to look at the Java UI API..
regards