In the updated version of the Rational UML modeling products, the UML2 plug-in contains the following package with public API:
The UML2 component contains the 2.1 metamodel (org.eclipse.uml2.uml). A binary plug-in that contains UML2 1.x API calls will not work in this version of the Rational UML modeling products. The source code for those plug-ins will have to be migrated to the new UML2 2.1 API in order to use the extensibility API for UML models (*.emx) and profiles (*.epx).
For a more detailed UML2 migration description, consult the Eclipse UML2
2.0 Migration Guide and UML2 2.1 Migration Guide at http://wiki.eclipse.org/MDT-UML2.