THIS IS EXPERIMENTAL! IT IS NOT OFFICIALLY SUPPORTED NEITHER BY RAP NOR BY EMF
EMFs runtime part should works out of the box with RAP as there are no dependencies to UI-related stuff. The only thing to be aware of is the dependency to the Eclipse Resources (aka Workspace).
EMF relies in the UI parts on the Resource infrastructure to support seamless integration with the Eclipse workspace. This is a big problem as the resource framework is multi-user enabled and thus can lead to problem in the RAP environment. Even if there may be workarounds available (eg. session-scoped EFS implementation), there is still only one workspace available. This can lead to big problems like a user who locks the workspace automatically locks all other users in the webapp.
As the whole EMF UI story has a strong dependency to the IDE bundle of Eclipse (org.eclipse.ui.ide), we need to support this somehow. This is rather problematic as IDE itself relies heavily on the Resource infrastructure. As simple mock is attached to the bug report stated in the References section.