Related. I am using the approach that notifications, Courses, and other portlets use to have a java data model.  The specific data sources would pull in their data however they do and incorporate it into the java data model, thus providing isolation and reuse.  The front end controller, service, and view tiers are thus isolated from details of a Peoplesoft v3, highly customized Peoplesoft v2, or other data source.

I think this type of strategy is required to maximize re-use and simplify integrations.  Note I did not go to the effort of insuring the java data model has all elements of the existing PS data model.  I was hoping that would happen as Wisconsin evolved their portlets.