This paper contributes a technique that expands the set of object invariants that one can reason about in modular verification. The technique uses history invariants, two-state invariants that describe the evolution of data values. The technique enables a flexible new way to specify and verify variations of the observer pattern, including iterators. The paper details history invariants and the new kind of object invariants, and proves a soundness theorem.

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In: ESOP

Publisher: Springer

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