The Prioritized Program Backlog plays a very similar role at the program level as the Prioritized Product Backlog does on project level. It identifies the requirements for the program and their priorities.
The items in the Prioritized Portfolio Backlog provide inputs to the various Prioritized Program Backlogs and, through Prioritized Program Backlogs, to Prioritized Product Backlogs of individual projects. As described for Prioritized Program Backlogs only minimal, if any, refinement of User Stories is done at this level, because the refinement is done in the projects and their specific Prioritized Product Backlogs.
There are a few differences, though:
The creation of the respective deliverables and their acceptance is done in the projects of the program. The done or acceptance criteria for each Product Backlog Item / User story may be defined on the program level. Projects have to adhere to them but can add their own criteria.
The length of a Sprint is project specific and, generally, varies from project to project in a program. In addition, the velocity of different teams is, normally, not the same. Therefore, it is not necessary to have very granular User Stories at the program level. The refinement of User Stories at the program level goes only far enough to ensure that the respective story is clearly understood and tangible acceptance criteria for the program can be defined.
