The biggest change is that the Java servlets previously corresponded to frames. Now there is effiectively one big XSLT script which potentially queries any of the servlets to produce the mashed up page. The programmer intends to refactor the big XSLT: the trouble with a single script is that it become difficult to have multiple programmers working on the code. But the project itself is fairly interesting: turning a c. 2000 state of the art HTML interface into a c. 2006 state-of-the-art XHTML interface with utterly different user interface from every aspect, but with no change to the XML-generating Java.
So even though the XML was designed with the idea “what information is needed by this frame in this application” once all the information for the application is exposed as XML by all the servlets, the information can be mashed up into an entirely new interface. It is the universal access to all the data that is the key here: that the data is exposed as a URL from a servlet using XML enables it too, but the fact the the data is open reduces the need to alter the Java “application logic”: indeed the “application logic” performed by the middle no longer reflects the application logic as perceived by the user, the connection between middleware servlet and frame no longer holding.