Mechanized operational semantics of WSL

This paper presents an experiment on computer assisted formal verification of program transformations. The operational semantics of WSL is formalized in the type theoretical proof assistant Coq, which forms the basis on which the correctness of program transformations can be stated and proved as formulae in Coq. A group of program transformations frequently used for software maintenance have been proved correct. The existence of a machine checked formal verification increases significantly the confidence in the correctness of program transformations, which is crucial for the reliability of software maintenance systems.