A boundary exception is a way to model possible errors or exceptions in a workflow model. A button will appear in the activity in which the error should be spotted. If this button is clicked, an alternate path in the workflow model will be executed.

By double-clicking an activity in which the error/exception the process-properties-popup will open. Then you have to select “Output” on the left side of the pop-up and click on the tab “Exceptions”. To create a new error you have to click on the red “flash”.

This will open a new pop-up with the name “Define error”. Here a new error/exception can be created and named. If a connection to another activity is created now, it will be marked as “exception-handling-connection” with a “flash” at the beginning of the connection.
If a user will see the activity in the ToDo client, a button with the name of the exception will appear. If a user clicks it, the modeled path for this exception will be executed.