Epsilon-covering is NP-complete

International audienceConsider the dilation and erosion of a shape S by a ball of radius ε. We call ε-covering of S any collection of balls whose union lies between the dilation and erosion of S. We prove that finding an ε-covering of minimum cardinality is NP-complete, using a reduction from vertex cover

Unification-free execution of TYPOL programs by semantic attribute evaluation

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Formalisation and Proofs of the Chilean Electronic Invoices System

We present the complete process of a formal specification and verification of the Chilean electronic invoice system which has been defined by the tax agency. We use this case study as a real-world and real-size example to illustrate our methodology for specification and verification of distributed applications. Our approach is based on a new hierarchical and parameterized model for synchronised networks of labelled transition systems. In this case study, we use a subset of the model as a graphical specification language. We check this formal specification of the invoice system against its informal requirements, described in terms of parameterized temporal logic formulas. Their satisfiability cannot be checked directly on the parameterized model\,: we introduce a method and a tool to instantiate the parameterized models and properties, allowing to use standard (finite-state, bisimulation-based) model-checkers for the verification. We also illustrate the use of different methods to avoid the state explosion problem by taking advantage of the parameterized structure and instantiations

A language and an Integrated Environment for Program Transformations

We present the TrfL language, a rule-based language designed for program transformations. For the end-user, TrfL is intended to support both direct manipulation in an interactive setting and automated execution in a stand-alon- e context. For the designer, the TrfL language features a high-level expressiv- e power based on powerful patterns, pre-conditions and post-actions, access to contextual information such as symbol tables or dataflow graphs, and functional composition of transformations. For the designer, we also provide an interactive environment for program transformations based on Centaur. This integrated environment makes it possible to build transformation rules by selection of syntax patterns of the object language and to automatically generate the TrfL source code. Static typechecking of TrfL rules is provided, to ensure correct construction of patterns, appropriate use of variables, and visibility rules in a program. Among numerous application domains (legacy code problems, static optimizations, parallelizations), we propose in this article a complete example based on partial evaluation techniques on a toy imperative language. Our final goal, with a formal description of the transformations, besides its interest per se, is to be able to provide tools for proving the correctness of the transformations, as well as other important properties (such as confluence, termination, etc)

Static Analysis of Java for Distributed and Parallel Programming

We investigate the use of static analysis for building distributed and parallel programs in Java. We first quickly explain a principle of seamless sequential, multithreaded and distributed programming using Java, in order to enhance code reuse and code evolution. We exhibit conditions on the graph of objects to detect activable objects and transform a sequential program into a distributed or parallel program using active objects. We then present a static analysis based on an abstract interpretation of a Java subset, which provides approximate sets of activable objects. Finally, we illustrate our algorithm and results with one example

Secured Information Flow for Asynchronous Sequential Processes

We present in this article a precise security model for data confidentiality in the framework of ASP (Asynchronous Sequential Processes). ASP is based on active objects, asynchronous communications, and data-flow synchronizations. We extend it with security levels attached to activities (active objects) and transmitted data. We design a security model that guarantees data confidentiality within an application; this security model takes advantages of both mandatory and discretionary access models. We extend the semantics of ASP with predicate conditions that provide a formal security framework, dynamically checking for unauthorized information flows. As a final result, all authorized communication paths are secure: no disclosure of information can happen. This theoretically-founded contribution may have a strong impact on distributed object-based applications, that are more and more present and confidentiality-demanding on the Internet, it also arises a new issue in data confidentiality: authorization of secured information flow transiting (by the mean of futures) through an unsecured Component

Biplanar Low-Dose Radiograph Is Suitable for Cephalometric Analysis in Patients Requiring 3D Evaluation of the Whole Skeleton

Background: The biplanar 2D/3D X-ray technology (BPXR) is a 2D/3D imaging system allowing simultaneous stereo-corresponding posteroanterior (PA) and lateral 2D views of the whole body. The aim of our study was to assess the feasibility of cephalometric analysis based on the BPXR lateral skull view to accurately characterize facial morphology. Method: A total of 17 landmarks and 11 angles were placed and/or calculated on lateral BPXR and lateral cephalograms of 13 patients by three investigators. Five methods of angle identification were performed: the direct construction of straight lines on lateral cephalograms (LC-A) and on BPXR (BPXR-A), as well as the calculation of angles based on landmark identification on lateral cephalograms (LA-L) and on BPXR with the PA image (BPXR-LPA) or without (BPXR-L). Intra- and interoperator reliability of landmark identification and angle measurement of each method were calculated. To determine the most reliable method among the BPXR-based methods, their concordance with the reference method, LC-A, was evaluated. Results: Both imaging techniques had excellent intra- and interoperator reliability for landmark identification. On lateral BPXR, BPXR-A presented the best concordance with the reference method and a good intra- and interoperator reliability. Conclusion: BPXR provides a lateral view of the skull suitable for cephalometric analysis with good reliability

Decreased respiratory-related postural perturbations at the cervical level under cognitive load

PURPOSE: In healthy humans, postural and respiratory dynamics are intimately linked and a breathing-related postural perturbation is evident in joint kinematics. A cognitive dual-task paradigm that is known to induce both postural and ventilatory disturbances can be used to modulate this multijoint posturo-ventilatory (PV) interaction, particularly in the cervical spine, which supports the head. The objective of this study was to assess this modulation. METHODS: With the use of optoelectronic sensors, the breathing profile, articular joint motions of the cervical spine, hip, knees and ankles, and centre of pressure (CoP) displacement were measured in 20 healthy subjects (37 years old [29; 49], 10 females) during natural breathing (NB), a cognitive dual task (COG), and eyes-closed and increased-tidal-volume conditions. The PV interaction in the CoP and joint motions were evaluated by calculating the respiratory emergence (REm). RESULTS: Only the COG condition induced a decrease in the cervical REm (NB: 17.2% [7.8; 37.2]; COG: 4.2% [1.8; 10.0] p = 0.0020) concurrent with no changes in the cervical motion. The CoP REm (NB: 6.2% [3.8; 10.3]; COG: 12.9% [5.8; 20.7] p = 0.0696) and breathing frequency (NB: 16.6 min-1 [13.3; 18.7]; COG: 18.6 min-1 [16.3; 19.4] p = 0.0731) tended to increase, while the CoP (p = 0.0072) and lower joint motion displacements (p < 0.05) increased. CONCLUSION: This study shows stable cervical spine motion during a cognitive dual task, as well as increased postural perturbations globally and in other joints. The concurrent reduction in the PV interaction at the cervical spine suggests that this "stabilization strategy" is centrally controlled and is achieved by a reduction in the breathing-related postural perturbations at this level. Whether this strategy is a goal for maintaining balance remains to be studied.This work was funded by the Chancellerie des Universités de Paris (Grant number: Legs Poix (LEG 1604)); ENS Cachan (Grant number: Ph.D. fellowship); Assistance Publique - Hôpitaux de Paris (Grant number: Grant “poste d’accueil APHP/Arts et Métiers” délé- gation à la Recherche Clinique et à l’Innovation (DRCI)); Paristech (Grant number: BiomeCAM chair)