Local Completeness Logic on Kleene Algebra with Tests

TL;DR

This paper extends Kleene algebra with tests (KAT) to represent Local Completeness Logic (LCL), enabling formal reasoning about program correctness and incorrectness within an algebraic framework, with proven soundness and completeness.

Contribution

It generalizes the algebraic representation of LCL using extended KATs with modal operators or top elements, unifying correctness and incorrectness reasoning.

Findings

Extended KATs can represent LCL triples.

LCL proof system is shown to be sound.

Under certain conditions, LCL proof system is complete.

Abstract

Local Completeness Logic (LCL) has been put forward as a program logic for proving both the correctness and incorrectness of program specifications. LCL is an abstract logic, parameterized by an abstract domain that allows combining over- and under-approximations of program behaviors. It turns out that LCL instantiated to the trivial singleton abstraction boils down to O'Hearn incorrectness logic, which allows us to prove the presence of program bugs. It has been recently proved that suitable extensions of Kleene algebra with tests (KAT) allow representing both O'Hearn incorrectness and Hoare correctness program logics within the same equational framework. In this work, we generalize this result by showing how KATs extended either with a modal diamond operator or with a top element are able to represent the local completeness logic LCL. This is achieved by studying how these extended KATs can be endowed with an abstract domain so as to define the validity of correctness/incorrectness LCL triples and to show that the LCL proof system is logically sound and, under some hypotheses, complete.