Automatically Discovering Hidden Transformation Chaining Constraints

Model transformations operate on models conforming to precisely defined metamodels. Consequently, it often seems relatively easy to chain them: the output of a transformation may be given as input to a second one if metamodels match. However, this simple rule has some obvious limitations. For instance, a transformation may only use a subset of a metamodel. Therefore, chaining transformations appropriately requires more information. We present here an approach that automatically discovers more detailed information about actual chaining constraints by statically analyzing transformations. The objective is to provide developers who decide to chain transformations with more data on which to base their choices. This approach has been successfully applied to the case of a library of endogenous transformations. They all have the same source and target metamodel but have some hidden chaining constraints. In such a case, the simple metamodel matching rule given above does not provide any useful information

Using Process Algebra to Statically Analyze Incremental Propagation Graphs

Active Operations are a set of operations that can be composed to build incremental bidirectional OCL-like expressions on collections. Each operation is capable of updating its result (resp. source) when a change occurs on its source (resp. result). The current implementation of active operations relies on the Observer design pattern to propagate changes from each operation to its successors. These relations form an implicit directed acyclic propagation graph. Previous work showed that this approach is limited and alignment issues appear in some situations. Several workarounds were proposed to mitigate these issues. In this work we present a new relational notation to describe propagation graphs. Along with this notation, we also present a new static analysis method of the propagation graph based on process algebra. This new method enables optimizations of the propagation graph not achievable with previous approaches, such as detection of parallelizable sections of the propagation graph or cache optimizations in specific situation

Quantum Hall resistance standards from graphene grown by chemical vapor deposition on silicon carbide

Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within $10^{-9}$ in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date, the required accuracy has been reported, only few times, in graphene grown on SiC by sublimation of Si, under higher magnetic fields. Here, we report on a device made of graphene grown by chemical vapour deposition on SiC which demonstrates such accuracies of the Hall resistance from 10 T up to 19 T at 1.4 K. This is explained by a quantum Hall effect with low dissipation, resulting from strongly localized bulk states at the magnetic length scale, over a wide magnetic field range. Our results show that graphene-based QHRS can replace their GaAs counterparts by operating in as-convenient cryomagnetic conditions, but over an extended magnetic field range. They rely on a promising hybrid and scalable growth method and a fabrication process achieving low-electron density devices.Comment: 12 pages, 8 figure

Typing in Model Management

International audienceModel management is essential for coping with the complexity introduced by the increasing number and varied nature of artifacts involved in MDE-based projects. Global Model Management (GMM) addresses this issue enabling the representation of artifacts, particularly transformation composition and execution, by a model called a megamodel. Typing information about artifacts can be used for preventing type errors during execution. In this work, we present a type system for GMM that improves its current typing approach and enables formal reasoning about the type of artifacts within a megamodel. This type system is able to capture non-trivial situations such as the use of higher order transformations

Formal Verification Integration Approach for DSML

International audienceThe application of formal methods (especially, model check- ing and static analysis techniques) for the verification of safety critical embedded systems has produced very good results and raised the inter- est of system designers up to the application of these technologies in real size projects. However, these methods usually rely on specific verifica- tion oriented formal languages that most designers do not master. It is thus mandatory to embed the associated tools in automated verification toolchains that allow designers to rely on their usual domain-specific modeling languages (DSMLs) while enjoying the benefits of these power- ful methods. More precisely, we propose a language to formally express system requirements and interpret verification results so that system designers (DSML end-users) avoid the burden of learning some formal verification technologies. Formal verification is achieved through trans- lational semantics. This work is based on a metamodeling pattern for executable DSML that favors the definition of generative tools and thus eases the integration of tools for new DSML