Formal specifications of software applications are hard to understand, even for domain experts. Because a formal specification is abstract, reading it does not immediately convey the expected behaviour of the software. Carefully chosen examples of the software’s behaviour, on the other hand, are concrete and easy to understand, but poorly-chosen examples are more confusing than helpful. In order to understand formal specifications, software developers need good examples.

We have created a method that automatically derives a suite of good examples from a formal specification. Each example is judged by our method to illustrate one feature of the specification. The generated examples give users a good understanding of the behaviour of the software. We evaluated our method by measuring how well students understood an API when given different sets of examples; the students given our examples showed significantly better understanding.