An ascertainment relation is an internal alternative relation in which a following proposition presents an alternative circumstance where a preparatory condition, of the illocutionary act that includes the previous proposition, is not met. The alternative is presented to make a query about the defectiveness or nondefectiveness of the illocutionary act.
Do you want a sandwich? Or, aren’t you hungry?
Congratulations with your new car. Or, aren’t you happy with it?
Shut up! Or, don’t you see I’m busy?