Modèle de contraintes temporelles pour systèmes polychrones

International audienceLa modélisation des systèmes répartis et des systèmes électroniques modernes nécessite des référentiels temporels multiples. Nous désignons ces systèmes sous le nom de “systèmes polychrones”. Le profil UML pour les systèmes temps réel et embarqués (MARTE) permet leur modélisation ainsi que la spécification de contraintes temporelles avec CCSL (Clock Constraint Specification Language). Dans MARTE, CCSL est non normatif et sa sémantique est informelle. Nous proposons ici une sémantique formelle en termes d'évolutions d'un “Time System” pour un noyau de CCSL. Un “Time System” est un modèle dynamique qui associe un ensemble de configurations à un modèle structurel constitué d'un ensemble d'horloges discrètes et de relations sur ces horloges. Les Time Systems sont comparés à d'autres modèles de causalités asynchrones, synchrones et polychrones. CCSL et sa mise en oeuvre sont illustrés sur un exemple de contrôleur d'ABS

Executing AADL models with UML/Marte

International audienceAADL and MARTE are two modeling formalisms supporting the analysis of real-time embedded systems. Since both cover similar aspects, a clear assessment of their respective strength and weakness is required. Building on previous works, we focus here on the time aspects of the two specifications. Relying on the MARTE Time Model and the operational semantics of its companion language CCSL we attempt to equipped UML activities with the execution semantics of an AADL specification. This is part of a much broader effort to build a generic simulator for UML models with the semantics explicitly defined within the model

Maxwell-Garnett mixing rule in the presence of multiple scattering: Derivation and accuracy

We give a rigorous and original derivation of the Maxwell-Garnett mixing rule in the dynamical regime for a composite dielectric random medium with small spherical inclusions. For certain configurations of scatterers, we show that contrarily to the common belief, the Maxwell-Garnett formula can remain very accurate at a high concentration of scatterers and incorporate multiple-scattering effects as well as attenuation of the mean field. We provide a realistic numerical example for which this is the case

Effective-medium theory for finite-size aggregates

We propose an effective-medium theory for random aggregates of small spherical particles that accounts for the finite size of the embedding volume. The technique is based on the identification of the first two orders of the Born series within a finite volume for the coherent field and the effective field. Although the convergence of the Born series requires a finite volume, the effective constants that are derived through this identification are shown to admit of a large-scale limit. With this approach we recover successively, and in a simple manner, some classical homogenization formulas: the Maxwell Garnett mixing rule, the effective-field approximation, and a finite-size correction to the quasi-crystalline approximation (QCA). The last formula is shown to coincide with the usual low-frequency QCA in the limit of large volumes, while bringing substantial improvements when the dimension of the embedding medium is of the order of the probing wavelength. An application to composite spheres is discussed

Modeling of Immediate vs. Delayed Data Communications: from AADL to UML MARTE

The original publication is available at http://www.ecsi-association.org/ecsi/main.asp?l1=library&fn=def&id=265International audienceThe forthcoming OMG UML Profile for Modeling and Analysis of Real-Time Embedded systems (MARTE) aims, amongst other things, at providing a referential Time Model subprofile where semantic issues can be explicitly and formally described. As a full-size exercise we deal here with the modeling of immediate and delayed data communications in AADL. It actually reflects an important issue in RT/E model semantics: a propagation of immediate communications may result in a combinatorial loop, with ill-defined behavior; introduction of delays may introduce races, which have to be controlled. We describe here the abilities of MARTE in this respect

On the semantics of UML/Marte Clock Constraints

Extended version available as a research report RR-6545International audienceUML goal of being a general-purpose modeling language discards the possibility to adopt too precise and strict a semantics. Users are to refine or define the semantics in their domain specific profiles. In the UML Profile for Modeling and Analysis of Real-Time and Embedded systems, we have defined a broadly expressive Time Model to provide a generic timed interpretation for UML models. Our clock constraint specification language supports the specification of systems with multiple clock domains. Starting with a priori independent clocks, we progressively compose them to get a family of possible executions. Our language supports both synchronous and asynchronous compositions, just like the synchronous language Signal, but also allows explicit non determinism. In this paper, we give a formal semantics to a core subset of MARTE clock constraint languages and we give an equivalent interpretation of this kernel in two other very different formal languages, Signal and Time Petri Nets

Non-functional property analysis using UML2.0 and model transformations

Real-time embedded architectures consist of software and hardware parts. Meeting non-functional constraints (e.g., real-time constraints) greatly depends on the mappings from the system functionalities to software and hardware components. Thus, there is a strong demand for precise architecture and allocation modeling, amenable to performance analysis. The report proposes a model-driven approach for the assessment of the quality of allocations of the system functionalities to the architecture. We consider two technical domains: the UML domain for the definition of the model elements (for both description and analysis), and an analysis domain, external to UML, used for formal verification. This report defines three meta-models, one for each domain, and provides automated transformations within and between these domains. A special attention is then paid to temporal property analysis, based on a particular analysis model: the Modular and Hierarchical Time Petri Nets

Multilevel Modeling Paradigm in Profile Definition

Building a UML profile entails defining concepts required to cover a specific domain, and then, using stereotypes to map domain concepts onto UML metaclasses. Capture of domain concepts with an object-oriented language (like UML) may be inappropriate, and may impede the mapping, where more than two modeling levels are required. Use of only classes and objects may introduce accidental complexity into the domain model if other modeling levels (e.g. metatype level) are necessary. In such situations, a multilevel paradigm with deep characterization and deep instantiation is recommended to reduce complexity. However, this paradigm deserves to be further explored, and its value for definition of UML profiles assessed. We therefore propose a solution to put in practice the multi-level paradigm within a standard UML 2.x tool. Our solution involves a semi-automatic process that transforms a model annotated with multi-level characteristics into a profile-based implementation. Such automation lessens the gap between domain model and implementation and ensures consistency. As an example, we have taken an excerpt from the MARTE time profile. We then describe the new design opportunities inherent in our process and show how this process facilitates both domain specification and profile definition

Un profil UML pour la modélisation multiniveau

Publié à TSI -- 29/2010. Ingénierie dirigée par les modèles - pp. 391--419 http://tsi.revuesonline.comBuilding a UML profile is tedious and error-prone. There is no precise methodology to guide the process. Best practices recommend gathering concepts in a technology-independent domain view before implementation. Still, the adequacy of the implementation should be verified. This paper proposes to transform automatically a domain model into a profile-based implementation. To reduce accidental complexity in the domain model and fully benefit from advanced profiling features in the generated profile, our process relies on the multilevel paradigm. The value of this paradigm for the definition of UML profiles is assessed and applied to a subset of the MARTE time model

On the Formal Execution of UML and DSL Models

International audienceModel-Driven Engineering intensively uses models and model transformations. Transformation tools ensure that the target model conforms to the target metamodel, so that it is syntactically correct. However, there is few assistance, or none at all, to guarantee that the semantics is preserved during the transformation. This is mainly due to the absence of an explicit semantics within the models. Models bring the syntax while the related (application-specific) analysis tools bring their own semantics. We propose here a model-driven approach to describe a formal and explicit semantics as a separate model. This formal semantics can then be attached to different UML /DSL models and a UML /DSL model can be executed with different semantics