code: public void setACModel(AbstractACModel<?> acModel, boolean notifyListeners) {
                  Validate.notNull(acModel);
                  if (this.acModel == acModel) {
                          return;
                  }
                  validateACModel(acModel);
                  this.acModel = acModel;
                  acModel.getContext().addContextListener(this);
                  if (notifyListeners) {
                          processContextListenerSupport.notifyACModelSet(acModel);
                  }
          }
docs: Sets the access control model which is used to determine authorized
  subjects for activity execution.<br>
  This method checks, if the access control model is compatible with
  the log context, i.e. is contains all subjects and activities of the
  log context.
  
  @param acModel An access control model.
  @param notifyListeners