title: Eclipse-RCP: How to add a plug-in with an application model into a perspective of a new RCP application?
body: <p>I am trying integrate several subsystems where each subsystem is developed as an E4 plug-in with its own application model for UI. I would like build a new RCP application with multiple perspectives and each perspective holds a subsystem. Subsystems may exchange some data, but not much.</p>
  
  <p>I am new to Eclipse RCP and just went through Lars Vogel's RCP tutorial. I still cannot totally understand how the framework works. Should I add subsystems as plug-ins or fragments? Do I need to define extension points in the final system and extensions in subsystem plug-ins? It seems that an application can only have one application model. If a plug-in application model cannot be added into another application, what's the right approach for my task?</p>