Abstract.
Auxiliary variables are essential for specifying programs in Hoare Logic. They are required to relate the value of variables in different states. However, the axioms and rules of Hoare Logic turn a blind eye to the role of auxiliary variables. We stipulate a new structural rule for adjusting auxiliary variables when strengthening preconditions and weakening postconditions. Courtesy of this new rule, Hoare Logic is adaptation complete, which benefits software re-use. This property is responsible for a number of improvements. Relative completeness follows uniformly from the Most General Formula property. Moreover, one can show that Hoare Logic subsumes Vienna Development Method's (VDM) operation decomposition rules in that every derivation in VDM can be naturally embedded in Hoare Logic. Furthermore, the new treatment leads to a significant simplification in the presentation for verification calculi dealing with more interesting features such as recursion.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Received October 1998 / Accepted in revised form October 1999
Rights and permissions
About this article
Cite this article
Kleymann, T. Hoare Logic and Auxiliary Variables. Form Aspects Comput 11, 541–566 (1999). https://doi.org/10.1007/s001650050057
Published:
Issue Date:
DOI: https://doi.org/10.1007/s001650050057