Verification of object-oriented programs with invariants

An object invariant defines what it means for an object’s data to be in a consistent state. Object invariants are central to the design and correctness of objectoriented programs. This paper defines a programming methodology for using object invariants, in which we enrich a program’s state space to express when each object invariant holds. The methodology deals with owned object components, ownership transfer, and subclassing, and is expressive enough to allow many interesting object-oriented programs to be specified and verified. Lending itself to sound modular verification, the methodology also provides a solution to the problem of determining what state a method is allowed to modify