33,231 research outputs found
Causal reasoning about distributed programs
We present an integrated approach to the specification, verification and testing of distributed programs. We show how global properties defined by transition axiom specifications can be interpreted as definitions of causal relationships between process states. We explain why reasoning about causal rather than global relationships yields a clearer picture of distributed processing.;We present a proof system for showing the partial correctness of CSP programs that places strict restrictions on assertions. It admits no global assertions. A process annotation may reference only local state. Glue predicates relate pairs of process states at points of interprocess communication. No assertion references auxiliary variables; appropriate use of control predicates and vector clock values eliminates the need for them. Our proof system emphasizes causality. We do not prove processes correct in isolation. We instead track causality as we write our annotations. When we come to a send or receive, we consider all the statements that could communicate with it, and use the semantics of CSP message passing to derive its postcondition. We show that our CSP proof system is sound and relatively complete, and that we need only recursive assertions to prove that any program in our fragment of CSP is partially correct. Our proof system is, therefore, as powerful as other proof systems for CSP.;We extend our work to develop proof systems for asynchronous communication. For each proof system, our motivation is to be able to write proofs that show that code satisfies its specification, while making only assertions we can use to define the aspects of process state that we should trace during test runs, and check during postmortem analysis. We can trace the assertions we make without having to modify program code or add synchronization or message passing.;Why, if we verify correctness, would we want to test? We observe that a proof, like a program, is susceptible to error. By tracing and analyzing program state during testing, we can build our confidence that our proof is valid
Fifty years of Hoare's Logic
We present a history of Hoare's logic.Comment: 79 pages. To appear in Formal Aspects of Computin
Formalizing Cyber--Physical System Model Transformation via Abstract Interpretation
Model transformation tools assist system designers by reducing the
labor--intensive task of creating and updating models of various aspects of
systems, ensuring that modeling assumptions remain consistent across every
model of a system, and identifying constraints on system design imposed by
these modeling assumptions. We have proposed a model transformation approach
based on abstract interpretation, a static program analysis technique. Abstract
interpretation allows us to define transformations that are provably correct
and specific. This work develops the foundations of this approach to model
transformation. We define model transformation in terms of abstract
interpretation and prove the soundness of our approach. Furthermore, we develop
formalisms useful for encoding model properties. This work provides a
methodology for relating models of different aspects of a system and for
applying modeling techniques from one system domain, such as smart power grids,
to other domains, such as water distribution networks.Comment: 8 pages, 4 figures; to appear in HASE 2019 proceeding
Theorem proving support in programming language semantics
We describe several views of the semantics of a simple programming language
as formal documents in the calculus of inductive constructions that can be
verified by the Coq proof system. Covered aspects are natural semantics,
denotational semantics, axiomatic semantics, and abstract interpretation.
Descriptions as recursive functions are also provided whenever suitable, thus
yielding a a verification condition generator and a static analyser that can be
run inside the theorem prover for use in reflective proofs. Extraction of an
interpreter from the denotational semantics is also described. All different
aspects are formally proved sound with respect to the natural semantics
specification.Comment: Propos\'e pour publication dans l'ouvrage \`a la m\'emoire de Gilles
Kah
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