Teaching the Construction of Correct Programs Using Invariant Based Programming

In most computer science curricula, formal reasoning about program correctness is taught separately from practical programming, and is thus by most students considered a purely theoretical activity. It has been a challenge to convince students of the practical applicability of formal methods. We present here an effort to apply Invariant Based Programming (IBP), a visual and practical program construction and verification methodology, in an introductory formal methods course as part of a pilot study at Åbo Akademi University. The course introduces a minimum of notational overhead, and allows the student to reason about correctness using mathematical concepts with which they are already familiar (such as set theory). We have used a programming environment with theorem prover support (SOCOS) to increase student confidence in the correctness of the program components that they construct. We evaluate the course using a mixed method approach, and provide data which show that IBP is well suited for teaching introductory formal methods.