ViewModels have a rooted AccessExpression that should return true or false (an empty value defaults to true). This expression controls whether the ViewModel is shown or not—the evaluation is done after any accessgroup evaluation. This expression complements the accessgroups as it checks the root objects' values and not only global values, as accessgroups do.

The AccessExpression can be checked before ViewModel creation with the OCL canAccess operator.

Note: Prior to 2021-02-01, the AccessExpression and AccessGroup.ViewEnableExpression had issues in both WPF and Turnkey—but are now fixed.