public class LinkAction implements IObjectActionDelegate {
	private ISelection selectedElement = null;
	
	public void selectionChanged(IAction action, ISelection selection) {
		action.setEnabled(false);
		if (selection instanceof IStructuredSelection == false || selection.isEmpty()) {
			return;
		}
		selectedElement = selection;
		action.setEnabled(true);
	}
	
	public void run(IAction action) {
	
		EObject source = null;
		ArrayList<EObject> targets = new ArrayList<EObject>();
		
		if (selectedElement != null) {
			for (Iterator<Object> i = ((IStructuredSelection) selectedElement).iterator (); i.hasNext ();) {
				Object k = i.next ();
				if (k instanceof aaaEditPart)
					source = ((aaaEditPart)k).resolveSemanticElement();
				else if (k instanceof bbbEditPart)
					targets.add (((bbbEditPart)k).resolveSemanticElement ());
			}
			
			if (source != null && targets.size() > 0) {				
				CreateRelationshipRequest request = new CreateRelationshipRequest(xxxElementTypes.Link_4001);
				LinkCreateCommand cmd = new LinkCreateCommand(request , (EObject)source, (EObject)targets.get(0));
				if (cmd.canExecute()) {
					try {
						cmd.execute(new NullProgressMonitor(), null);
					} catch (ExecutionException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
			}
		}
	}
}

request.setSource(source);
request.setTarget(targets.get(0));