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Spécification formelle de systèmes temps réel répartis par une approche flots de données à contraintes temporelles

Abstract : Real time systems are usually defined as systems where the total correctness of an operation depends not only on its logical correctness, but also on the execution time. Under this definition, time constraints are defined according to system operations. Another definition of real time systems is centered on data where the correctness of a system depends on the timed correctness of its data and of the data flows across the system. i.e. we expect the values taken by the variable to be regularly renewed and to be consistent with the environment and the other variables. I propose a modeling framework based on this later definition. This approach allows users to focus on specifying time constraints attached to data and to postpone task and communication scheduling matters. The timed requirements are not expressed as constraints on the implantation mechanism, but on the relations binding the system's variables. These relations between data are expressed in terms of a so called observation relation which abstracts the relation between the values that are taken by some variables, the set of sources and the image. This relation abstracts the communication as well as the computational operations and a set of observation relations models the system architecture and the data flows by defining the paths along which values of sources are propagated to build the values of an image. The real time properties are expressed as constraints on the propagation paths and state the temporal validity of the values. This temporal validity is defined by the time shift between the source and the image, and specifies the propagation of timely sound values along the path to build temporally correct values of the system outputs. At this level of abstraction, the designer gives a specification of the system based on timed properties about the timeline of data such as their freshness, stability, latency etc. In order to prove the feasibility of an observation-based model, a finite state transition system bi-similar with the specification is built. The existence of a finite bi-similar system is deduced from the bounded time shift between the variables. The existence of an infinite execution in this system proves the feasibility of the specification.
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https://tel.archives-ouvertes.fr/tel-00472469
Contributor : Tanguy Le Berre <>
Submitted on : Monday, April 12, 2010 - 11:12:46 AM
Last modification on : Thursday, March 26, 2020 - 6:33:58 PM
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Tanguy Le Berre. Spécification formelle de systèmes temps réel répartis par une approche flots de données à contraintes temporelles. Génie logiciel [cs.SE]. Institut National Polytechnique de Toulouse - INPT, 2010. Français. ⟨tel-00472469⟩

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