On structuring flowcharts (Preliminary Version)

Kosaraju, S. Rao

doi:10.1145/800113.803637

Cited by 2 publications

(2 citation statements)

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“…The introduction of additional variables is comparable in many ways to the elimination of goto statements in sequential programs that has been intensively discussed [BoJa66,AsMa71,BrSt72,Kosa73,Kosa76,Mill75,Elgo76] in the past. By the mentioned results, it turned out that every program with goto statements can be rewritten to an equivalent program without goto statements using only 'structured' statements like assignments, sequences, conditionals and loops.…”

Section: Impossibility Of Transforming General Quartz Programs To Sstmentioning

confidence: 99%

“…As the structure of the original program is thereby almost completely destroyed, it was a natural question whether the elimination of goto statements could still be done without using additional local variables. The question was negatively answered by different authors [AsMa71,BrSt72,Kosa73,Kosa76]. These proofs could not applied directly to synchronous programs since several ideas used there do not work for synchronous programs.…”

Section: Impossibility Of Transforming General Quartz Programs To Sstmentioning

confidence: 99%

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Interactive verification of synchronous systems

Gesell

Schneider

2012

Tenth ACM/IEEE International Conference on Formal Methods and Models for Codesign (MEMCODE2012)

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Embedded systems, ranging from very simple systems up to complex controllers, may nowadays have quite challenging real-time requirements. Many embedded systems are reactive systems that have to respond to environmental events and have to guarantee certain real-time constrain. Their execution is usually divided into reaction steps, where in each step, the system reads inputs from the environment and reacts to these by computing corresponding outputs.The synchronous Model of Computation (MoC) has proven to be well-suited for the development of reactive real-time embedded systems whose paradigm directly reflects the reactive nature of the systems it describes. Another advantage is the availability of formal verification by model checking as a result of the deterministic execution based on a formal semantics. Nevertheless, the increasing complexity of embedded systems requires to compensate the natural disadvantages of model checking that suffers from the well-known state-space explosion problem. It is therefore natural to try to integrate other verification methods with the already established techniques. Hence, improvements to encounter these problems are required, e.g., appropriate decomposition techniques, which encounter the disadvantages of the model checking approach naturally. But defining decomposition techniques for synchronous language is a difficult task, as a result of the inherent parallelism emerging from the synchronous broadcast communication.Inspired by the progress in the field of desynchronization of synchronous systems by representing them in other MoCs, this work will investigate the possibility of adapting and use methods and tools designed for other MoC for the verification of systems represented in the synchronous MoC. Therefore, this work introduces the interactive verification of synchronous systems based on the basic foundation of formal verification for sequential programs -the Hoare calculus. Due to the different models of computation several problems have to be solved. In particular due to the large amount of concurrency, several parts of the program are active at the same point of time. In contrast to sequential programs, a decomposition in the Hoare-logic style that is in some sense a symbolic execution from one control flow location to another one requires the consideration of several flows here. Therefore, different approaches for the interactive verification of synchronous systems are presented.Additionally, the representation of synchronous systems by other MoCs and the influence of the representation on the verification task by differently embedding synchronous system in a single verification tool are elaborated.The feasibility is shown by integration of the presented approach with the established model checking methods by implementing the AIFProver on top of the Averest system.

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