Applying theorem discovery to automatically find and check usability heuristics

Theorem discovery is a novel technique for the automatic analysis of statespace-based models of user interfaces, in which possible sequences of user actions are systematically computed and compared for equivalence, or close equivalence, of effect. Using this technique, we noticed a previously undetected problem with the behaviour of many widely-used inexpensive off-the-shelf interactive devices. Specifically, on many calculators, pressing the decimal point key has no effect on the display, thus unnecessarily breaking the well known usability heuristic that an interactive system should provide appropriate feedback to the user, and potentially causing unnecessary confusion that may lead to error. While this insight is interesting in itself, it is also of significance as a simple but nonetheless non-trivial example of the power and potential of theorem discovery as an analytical technique, not least because the problem - obvious once pointed out - has apparently remained undetected and unremarked upon for many years.