Exception flow in the process model

Since any BPM tool like Appian follows BPMN Standards, I wonder why we don't have the error event in Appian process models. If I want to handle errors or exceptions in process models, how can I do it..?? for example :

I have a write to data store entity smart service in my process model and for some reason like data length exceeds, the activity got failed, now in this situation, I want to add a exception flow which will create a user task to correct the entered data

or

lets say in my process model, I have an activity which is not so important, but if it fails to execute I don't want my process model to be paused, I want it to continue further ( we can do this in Appian by making the acitivity as subprocess, but is there any other way to avoid the subprocess)