Model checking: Algorithmic verification and debugging

Turing Lecture from the winners of the 2007 ACM A.M. Turing Award.In 1981, Edmund M. Clarke and E. Allen Emerson, working in the USA, and Joseph Sifakis working independently in France, authored seminal papers that founded what has become the highly successful field of model checking. This verification technology provides an algorithmic means of determining whether an abstract model-representing, for example, a hardware or software design-satisfies a formal specification expressed as a temporal logic (TL) formula. Moreover, if the property does not hold, the method identifies a counterexample execution that shows the source of the problem.The progression of model checking to the point where it can be successfully used for complex systems has required the development of sophisticated means of coping with what is known as the state explosion problem. Great strides have been made on this problem over the past 28 years by what is now a very large international research community. As a result many major hardware and software companies are beginning to use model checking in practice. Examples of its use include the verification of VLSI circuits, communication protocols, software device drivers, real-time embedded systems, and security algorithms.The work of Clarke, Emerson, and Sifakis continues to be central to the success of this research area. Their work over the years has led to the creation of new logics for specification, new verification algorithms, and surprising theoretical results. Model checking tools, created by both academic and industrial teams, have resulted in an entirely novel approach to verification and test case generation. This approach, for example, often enables engineers in the electronics industry to design complex systems with considerable assurance regarding the correctness of their initial designs. Model checking promises to have an even greater impact on the hardware and software industries in the future.-Moshe Y. Vardi, Editor-in-Chief

Preserving Topology and Elasticity for Embedded Deformable Models

International audienceIn this paper we introduce a new approach for the embedding of linear elastic deformable models. Our technique results in significant improvements in the efficient physically based simulation of highly detailed objects. First, our embedding takes into account topological details, that is, disconnected parts that fall into the same coarse element are simulated independently. Second, we account for the varying material properties by computing stiffness and interpolation functions for coarse elements which accurately approximate the behaviour of the embedded material. Finally, we also take into account empty space in the coarse embeddings, which provides a better simulation of the boundary. The result is a straightforward approach to simulating complex deformable models with the ease and speed associated with a coarse regular embedding, and with a quality of detail that would only be possible at much finer resolution

Adaptive tearing and cracking of thin sheets

This paper presents a method for adaptive fracture propagation in thin sheets. A high-quality triangle mesh is dynamically restructured to adaptively maintain detail wherever it is required by the simulation. These requirements include refining where cracks are likely to either start or advance. Refinement ensures that the stress distribution around the crack tip is well resolved, which is vital for creating highly detailed, realistic crack paths. The dynamic meshing framework allows subsequent coarsening once areas are no longer likely to produce cracking. This coarsening allows efficient simulation by reducing the total number of active nodes and by preventing the formation of thin slivers around the crack path. A local reprojection scheme and a substepping fracture process help to ensure stability and prevent a loss of plasticity during remeshing. By including bending and stretching plasticity models, the method is able to simulate a large range of materials with very different fracture behaviors. Copyright © ACM

TAXYS: a tool for the development and verification of real-time embedded systems

The correct behavior of real-time applications depends not only on the correctness of the results of computations but also on the times at which these results are produced. As a matter of fact, violations of real-time constraints in embedded systems are the most difficult errors to detect, because they are extremely sensitive both to the patterns of external events stimulating the system and to the timing behavior of the system itself. Clearly, the development of realtime systems requires rigorous methods and tools to reduce development costs and "time-to-market" while guaranteeing the quality of the produced code (in particular, respect of the temporal constraints). The above requirements motivated the development of the TAXYS tool, dedicated to the design and validation of real-time telecommunications software. One of the major goal of the TAXYS tool is to produce a formal model that captures the temporal behavior of the whole application which is composed of the embedded computer and its external environment. For this purpose we use the formal model of timed automata. The choice of this model allows the use of results, algorithms and tools available. Here, we use the KRONOS model checker for model analysis. From the source code of the application, an ESTEREL program annotated with temporal constraints, the TAXYS tool produces on one hand a sequential executable code and on the other hand a timed model of the application. This model is again composed with a timed model of the external environment in order to obtain a global model which is statically analyzed to validate timing constraints. This validation should notably shorten design time by limiting tedious test and simulation session

Contract Aware Components, 10 years after

The notion of contract aware components has been published roughly ten years ago and is now becoming mainstream in several fields where the usage of software components is seen as critical. The goal of this paper is to survey domains such as Embedded Systems or Service Oriented Architecture where the notion of contract aware components has been influential. For each of these domains we briefly describe what has been done with this idea and we discuss the remaining challenges.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Global Englishes language teaching:Bottom-up curriculum implementation

In today's globalised world, the needs of English language learners have changed, particularly those learning to use the English language as a lingua franca. Growing research showcasing the global use of English as a lingua franca (ELF), the creativity of ELF users, and the diverse ways in which they negotiate successful communication in multilingual encounters has numerous implications for the field of TESOL. This article reports on a study with preservice and in‐service TESOL practitioners taking a Global Englishes for Language Teaching (GELT) option course in a 1‐year Master's in TESOL programme at a Russell Group university in the United Kingdom. The study explores attitudes towards GELT but also towards the proposals for, and barriers to, curriculum innovation as well as factors influencing such attitudes. Interviews (n = 21) and questionnaires (n = 47) revealed that attitudes remain norm bound, yet the study revealed a positive orientation towards GELT and provided insights into the feasibility of GELT‐related curriculum innovation and teacher education syllabus design. The study calls for more research with preservice and in‐service TESOL practitioners at different stages of the innovation process to ensure successful and sustainable GELT curricular innovation

The methodology of surveillance for antimicrobial resistance and healthcare-associated infections in Europe (SUSPIRE): a systematic review of publicly available information.

OBJECTIVES: Surveillance is a key component of any control strategy for healthcare-associated infections (HAIs) and antimicrobial resistance (AMR), and public availability of methodologic aspects is crucial for the interpretation of the data. We sought to systematically review publicly available information for HAIs and/or AMR surveillance systems organized by public institutions or scientific societies in European countries. METHODS: A systematic review of scientific and grey literature following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines was performed. Information on HAIs and/or AMR surveillance systems published until 31 October 2016 were included. RESULTS: A total of 112 surveillance systems were detected; 56 from 20 countries were finally included. Most exclusions were due to lack of publicly available information. Regarding AMR, the most frequent indicator was the proportion of resistant isolates (27 of 34 providing information, 79.42%); only 18 (52.9%) included incidence rates; the data were only laboratory based in 33 (78.5%) of the 42 providing this information. Regarding HAIs in intensive care units, all 22 of the systems providing data included central line-associated bloodstream infections, and 19 (86.3%) included ventilator-associated pneumonia and catheter-associated urinary tract infections; incidence density was the most frequent indicator. Regarding surgical site infections, the most frequent procedures included were hip prosthesis, colon surgery and caesarean section (21/22, 95.5%). CONCLUSIONS: Publicly available information about the methods and indicators of the surveillance system is frequently lacking. Despite the efforts of European Centre for Disease Control and Prevention (ECDC) and other organizations, wide heterogeneity in procedures and indicators still exists