ASSERT: a step towards reliable and scientific system and software engineering.

International audienceThe ASSERT (www.assert-project.org) project (Automated proof-based System and Software Engineering for Real-Time systems) is an integrated project partially funded by the European Commission within the Information Society Technologies priority of the 6th Framework Program in the area of embedded systems. The project is coordinated by the European Space Agency (ESA) in the TEC directorate (Technical and Quality management), Software Systems division. The assert consortium is made of 28 partners (see the full list in section 7) representing the space industry, research laboratories, software houses and tool developers. The project started in September 2004 and has ended in December 2007. The main objective of ASSERT is to change the way system and software engineering is performed today to adopt a more reliable and scientific approach based on modelling, preservation of system properties and model transformation down to the final code.The current results include a process, a set of tool prototypes and case studies demonstrating the validity of the overall approach. The project results will now be disseminated in operational projects through the support of ESA, the tool and technologies providers and the industrialists from the space sector

The TASTE Toolset: turning human designed heterogeneous systems into computer built homogeneous software.

The TASTE tool-set results from spin-off studies of the ASSERT project, which started in 2004 with the objective to propose innovative and pragmatic solutions to develop real-time software. One of the primary targets was satellite flight software, but it appeared quickly that their characteristics were shared among various embedded systems. The solutions that we developed now comprise a process and several tools ; the development process is based on the idea that real-time, embedded systems are heterogeneous by nature and that a unique UML-like language was not helping neither their construction, nor their validation. Rather than inventing yet another "ultimate" language, TASTE makes the link between existing and mature technologies such as Simulink, SDL, ASN.1, C, Ada, and generates complete, homogeneous software-based systems that one can straightforwardly download and execute on a physical target. Our current prototype is moving toward a marketed product, and sequel studies are already in place to support, among others, FPGA systems

Synthèse et rôle de l'oxyde nitrique d'origine bactérienne dans la symbiose fixatrice d'azote Ensifer meliloti/Medicago truncatula

Le monoxyde d’azote (NO) est une petite molécule gazeuse extrêmement réactive intervenant dans de nombreux processus biologiques. Dans les interactions hôte-pathogènes, le NO peut être produit par les deux partenaires et fait partie de l'arsenal de défense de l'hôte tout comme il fait aussi partie des armes d'attaque du pathogène. Les pathogènes se sont aussi adaptés en mettant en place des systèmes de réponse au NO produit par l'hôte. Dans les interactions symbiotiques plante-microorganismes, du NO a été également détecté. C’est le cas durant la symbiose fixatrice d’azote entre la bactérie Ensifer meliloti et la légumineuse Medicago truncatula. Dans cette interaction il a été montré que non seulement le NO est important lors de l'infection par le symbionte, mais qu'il peut aussi avoir un rôle à des étapes plus tardives comme lors de la fixation d'azote ou de la senescence nodulaire. Dans les nodules, le NO est produit par les deux partenaires avec une contribution d’environ 30% pour la bactérie. Chez la plante, des travaux récents ont montré que la synthèse de NO reposait en grande partie sur des nitrate réductases couplées à la chaine mitochondriale de transfert d'électrons. Coté bactérien, seule la voie de dénitrification était connue comme voie de synthèse possible du NO. Ce travail de thèse pose deux questions centrales : Quelles sont les voies de synthèse du NO chez E. meliloti ? et quel est le rôle du NO produit par les bactéries dans l'interaction symbiotique ? Nous avons montré que E. meliloti ne possède pas de NO synthase capable de produire du NO comme il en existe chez certaines bactéries pathogènes. Seule la voie de dénitrification est responsable de la synthèse du NO chez E. meliloti en vie libre et durant la symbiose. Nous avons aussi montré que la bactérie possède une voie assimilatrice du nitrate fonctionnelle, permettant de contribuer à la production de NO en augmentant la quantité de nitrite disponible pour alimenter la voie de dénitrification. La voie assimilatrice est active aussi bien en aérobie qu'en conditions micro-aérobiques mais ne contribuerait pas à la production de NO dans les nodules symbiotiques. Des résultats préliminaires montrent que cette voie serait régulée par un système à deux composants mais aussi, de façon originale, par un ARN non codant. Enfin nous avons montré que le NO produit par la bactérie ne présente pas de rôle essentiel, ni durant les étapes précoces, ni dans les étapes plus tardives de la symbiose. L'ensemble des résultats nous permet de proposer un modèle des voies de production de NO chez E. meliloti et suggère que dans les interactions symbiotiques le NO bactérien ne joue pas un rôle aussi déterminant que dans les interactions hôtes-pathogènes.Nitric oxide (NO) is a small, highly reactive gaseous molecule involved in many biological processes. In host-pathogen interactions, NO can be produced by both partners and is part of the host defense arsenal but can also be used by the pathogen as a weapon for a successful infection. In addition, pathogens have evolved responses consisting in adaptation to NO or degradation of this toxic molecule. In symbiotic plant-microorganism interactions, NO has also been detected. Indeed, during the nitrogen-fixing symbiosis between the bacterium Ensifer meliloti and the model legume Medicago truncatula, it has been shown that not only NO is important during the infection of the plant root by the symbiont, but also that it can play a role at later stages such as during nitrogen fixation or nodule senescence. In nodules, NO is produced by both partners with a contribution of about 30% by the bacteria. In plants, recent work has shown that NO synthesis is essentially based on nitrate reductases coupled to the mitochondrial electron transfer chain. On the bacterial side, only the denitrification pathway was known as a possible NO synthesis pathway. This thesis work focuses on two main questions: Are there different NO synthesis pathways in E. meliloti ? and what is the role of bacterial NO in the symbiotic interaction? We have shown that E. meliloti does not possess a NO synthase capable of producing NO as it can be found in some pathogenic bacteria. Denitrification is the only pathway involved in NO synthesis in E. meliloti either in its free life or during symbiosis. We have also shown that the bacterium displays a functional nitrate assimilatory pathway which contributes to NO production by increasing the amount of nitrite available to feed the denitrification pathway. The assimilatory pathway is active under both aerobic and microaerobic conditions, however it does not contribute to NO production in symbiotic root nodules of legumes. Preliminary results show that this pathway is regulated by a two-component system but could also be regulated by a non-coding RNA. Finally, we have shown that NO produced by the bacterium does not play an essential role, neither during the early stages, nor in the later stages of symbiosis. Altogether, these results allow us to propose a model of the NO production pathways in E. meliloti and suggest that in symbiotic interactions, bacterial NO does not play such a determining role as observed in host-pathogen interactions

The TASTE Toolset: turning human designed heterogeneous systems into computer built homogeneous software

International audienceThe TASTE tool-set results from spin-off studies of the ASSERT project, which started in 2004 with the objective to propose innovative and pragmatic solutions to develop real-time software. One of the primary targets was satellite flight software, but it appeared quickly that their characteristics were shared among various embedded systems. The solutions that we developed now comprise a process and several tools ; the development process is based on the idea that real-time, embedded systems are heterogeneous by nature and that a unique UML-like language was not helping neither their construction, nor their validation. Rather than inventing yet another "ultimate" language, TASTE makes the link between existing and mature technologies such as Simulink, SDL, ASN.1, C, Ada, and generates complete, homogeneous software-based systems that one can straightforwardly download and execute on a physical target. Our current prototype is moving toward a marketed product, and sequel studies are already in place to support, among others, FPGA systems

Identification of CpG island at the 5' end of murine leukemia inhibitory factor gene

AbstractWe identified a CpG island at the 5' end of murine leukemia inhibitory factor gene (LIF). The CpG island is 0.6 kb long and covers most of the first exon and first intron. The region is non-methylated, its G+C content is 65% and relative frequency of CpG dinucleotide is 0.7. The block of 150 nucleotides, which is 72% conserved between murine, human, ovine and porcine genes, is a part of the CpG island. Two DNA fragments from this CpG island interact with nuclear proteins from NIH 3T3 cells. One fragment partially covers the block of conserved nucleotides. Human, ovine and porcine LIF genes also contain G+C- and CpG-rich sequences in the corresponding region

Extending ASSERT for HW/SW Co-design

Embedded systems are commonly designed by specifying and developing hardware and software systems separately. On the contrary, the hardware/software (HW/SW) co-development exploits the trade-offs between hardware and software in a system through their concurrent design. HW/SW Codevelopment techniques take advantage of the flexibility of system design to create architectures that can meet stringent performance requirements with a shorter design cycle. This paper presents the work done within the scope of ESA HWSWCO (Hardware-Software Co-design) study. The main objective of this study has been to address the HW/SW co-design phase to integrate this engineering task as part of the ASSERT process (refer to [1]) and compatible with the existing ASSERT approach, process and tool, Advances in the automation of the design of HW and SW and the adoption of the Model Driven Architecture (MDA) [9] paradigm make possible the definition of a proper integration substrate and enables the continuous interaction of the HW and SW design paths

Integration of formal fault analysis in ASSERT: Case studies and lessons learnt

International audienceThe ASSERT European Integrated Project (Automated proof-based System and Software Engineering for Real-Time systems; EC FP6, IST-004033) has investigated, elaborated and experimented advanced methods based on the AltaRica language and support tool OCAS for architecture and fault approach propagation description analysis, and integrated in the complete ASSERT process. The paper describes lessons learnt from three case studies: safety critical spacecraft, autonomous deep exploration spacecraft, and civil aircraft

Алгоритм и математическая модель геометрического позиционирования асферического составного зеркала

In recent years, the largest terrestrial and orbital telescopes operating in a wide spectral range of wavelengths use the technology of segmented composite elements to form the main mirror. This approach allows: to expand the spectral operating range from 0.2 to 11.0 μm and to increase the diameter of the entrance pupil of the receiving optical system, while maintaining the optimal value of the exponent mS– mass per unit area.Two variants of adjusting the position of mirror segments are considered when forming an aspherical surface of the second order, with respect to the base surface of the nearest sphere, including geometrical and opto-technical positioning.The purpose of the research was to develop an algorithm for solving the problem of geometric positioning of hexagonal segments of a mirror telescope, constructing an optimal circuit for traversing elements when aligning to the nearest radius to an aspherical surface, and also to program the output calculation parameters to verify the adequacy of the results obtained.Various methods for forming arrays from regular hexagonal segments with equal air gaps between them are considered. The variant of construction of arrays through concentric rings of an equal step is offered.A sequential three-step method for distributing mosaic segments is presented when performing calculations for aligning the aspherical surface: multipath linear; multipath point; block trapezoidal.In the course of mathematical modeling an algorithm was developed to solve the problem of geometric positioning of flat hexagonal segments of a mirror telescope. In the Python programming language, program loops are designed to form the data array necessary to construct a specular reflective surface of a given aperture. In the software package Zemax, the convergence of optical beams from flat hexagonal elements to the central region of the aspherical surface is verified. В последние годы крупнейшие наземные и орбитальные телескопы, работающие в широком спектральном диапазоне длин волн, при формировании главного зеркала используют технологию сегментированных составных элементов. Такой подход позволяет: расширить спектральный рабочий диапазон от 0,2 до 11,0 мкм и увеличить диаметр входного зрачка приемной оптической системы, при сохранении оптимального значения показателя mS – масса на единицу площади. Цель исследований заключалась в разработке алгоритма для решения задачи геометрического позиционирования гексагональных сегментов зеркального телескопа, построения оптимальной схемы «обхода» элементов при юстировке на ближайший радиус к асферической поверхности, а также программной апробации выходных расчетных параметров с целью проверки адекватности полученных результатов.Рассмотрены два варианта юстировки положения зеркальных сегментов при формировании асферической поверхности второго порядка, относительно базовой поверхности ближайшей сферы, включающие геометрическое и оптотехническое позиционирование.Рассмотрены различные методики формирования массивов из регулярных шестиугольных сегментов с равными воздушными промежутками между ними. Предложен вариант построения массивов через концентрические кольца равного шага.Представлена последовательная трехступенчатая методика распределения сегментов мозаики при выполнении расчетов по юстировке асферической поверхности: многолучевая линейная; многолучевая точечная; блочная трапецеидальная.В ходе проведения математического моделирования разработан алгоритм для решения задачи геометрического позиционирования плоских гексагональных сегментов зеркального телескопа. На языке программирования Python составлены циклы программы для формирования массива данных необходимых для построения зеркальной отражающей поверхности заданной апертуры. В программном пакете Zemax выполнена проверка сходимости оптических лучей от плоских гексагональных элементов в центральную область асферической поверхности