6 research outputs found
Formal proof in network calculus
De nos jours les avions ne peuvent se passer d'un important rĂ©seau embarquĂ© pour faire communiquer les nombreux capteurs et actionneurs qui y sont dissĂ©minĂ©s. Ces rĂ©seaux ayant une fonction critique, en particulier pour les commandes de vol, il est important d'en garantir certaines propriĂ©tĂ©s telles des dĂ©lais de traversĂ©e ou l'absence de dĂ©bordement de buffers. Le calcul rĂ©seau est une mĂ©thode mathĂ©matique permettant de rĂ©aliser de telles preuves [2]. Elle a jouĂ© un rĂŽle clef dans la certification du rĂ©seau AFDX, dĂ©rivĂ© de l'ethernet, utilisĂ© Ă bord des avions les plus rĂ©cents (A380, A350).Le Calcul RĂ©seau se base sur des rĂ©sultats mathĂ©matiques utilisant l'algĂšbre tropicale. Ces rĂ©sultats sont relativement simple mais dĂ©jĂ bien assez subtiles pour qu'il soit trĂšs facile de commettre des erreurs ou des omissions lors de preuves papier ou de calcul de valeur concrĂštes. Par ailleurs, les assistants de preuve sont un bon outil pour rĂ©aliser une vĂ©rification mĂ©canique de ce genre de preuves et obtenir un trĂšs haut niveau de confiance dans leurs rĂ©sultats. Nous formalisons donc avec un tel outil les notions et propriĂ©tĂ©s fondamentales de la thĂ©orie du Calcul RĂ©seau. Ces rĂ©sultats font intervenir des propriĂ©tĂ©s sur les nombres rĂ©els, tel que des bornes supĂ©rieures et des limites de fonctions linĂ©aires donc nous souhaitons utiliser un outil de formalisation capable d'implĂ©menter untel niveau mathĂ©matique. Nous utilisons l'assistant de preuve Coq. Il s'agit d'un outil disposant dĂ©jĂ d'un long dĂ©veloppement dont la librairie Mathematical Components qui permet de formaliser de l'analyse sur les nombres rĂ©els et la construction de structures algĂ©briques comme celles utilisĂ©es dans le Calcul RĂ©seau. Le calcul de valeurs effective repose sur des opĂ©rations de l'algĂšbre min-plus sur des fonctions rĂ©elles. Des algorithmes sur des sous-ensembles spĂ©cifiques peuvent ĂȘtre trouvĂ©s dans la littĂ©rature [3]. De tels algorithmes et leurs implĂ©mentations sont toutefois compliquĂ©s. PlutĂŽt que de dĂ©velopper une preuve de la bonne implĂ©mentation de ces algorithmes, nous prenons une implĂ©mentation existante comme Oracle et nous donnons des critĂšres de vĂ©rifications en Coq.[1] Anne Bouillard, Marc Boyer et Euriell Le Corronc. DeterministicNetwork Calculus : From Theory to Practical Implementation. John Wiley& Sons, Ltd, oct. 2018[2] Assia Mahboubi et Enrico Tassi. Mathematical Components. Zenodo,jan. 2021[3] Anne Bouillard et Eric Thierry. « An Algorithmic Toolbox forNetwork Calculus ». In : Discret. Event Dyn. Syst. 18.1 (2008),p. 3-49.Nowadays aircrafts need a large on-board network to enable themany sensors and actuators disseminated in them to communicate with one another.Since these networks have a critical function, particularly for flight controls,it is important to guarantee certain properties such as crossingdelays or the absence of buffer overflows. Network calculus is amathematical method for performing such proofs. It played a keyrole in the certification of AFDX networks, derived from ethernet, used onboard the most recent aircrafts (A380, A350).Network Calculus is based on relatively simple mathematicalresults but already quite subtle enough that it is very easy to geterrors or omissions during pen and paper proofs. Moreover, proof assistantsare a good tool for mechanically checking such proofs and obtaininga very high level of confidence in their results.We formalize with this tool the fundamental propertiesunderlying the theory of Network Calculus. These results involverelatively basic properties on real numbers, such as upper bounds oreven limits of piecewise linear functions. We use the Coqproof assistant as well as the Mathematical components library.Effective computations rely on operators from the min-plus algebra onreal functions. Algorithms on specific subsets can be found in theliterature. Such algorithms and related implementations arehowever complicated. Instead of redeveloping a provably correctimplementation, we take an existing implementation as an oracle andpropose a Coq based verifier.Anne Bouillard, Marc Boyer et Euriell Le Corronc. DeterministicNetwork Calculus : From Theory to Practical Implementation. John Wiley& Sons, Ltd, oct. 2018Assia Mahboubi et Enrico Tassi. Mathematical Components. Zenodo,jan. 2021Anne Bouillard et Eric Thierry. « An Algorithmic Toolbox forNetwork Calculus ». In : Discret. Event Dyn. Syst. 18.1 (2008),p. 3-49
Preuve formelle en calcul réseau
Nowadays aircrafts need a large on-board network to enable themany sensors and actuators disseminated in them to communicate with one another.Since these networks have a critical function, particularly for flight controls,it is important to guarantee certain properties such as crossingdelays or the absence of buffer overflows. Network calculus is amathematical method for performing such proofs. It played a keyrole in the certification of AFDX networks, derived from ethernet, used onboard the most recent aircrafts (A380, A350).Network Calculus is based on relatively simple mathematicalresults but already quite subtle enough that it is very easy to geterrors or omissions during pen and paper proofs. Moreover, proof assistantsare a good tool for mechanically checking such proofs and obtaininga very high level of confidence in their results.We formalize with this tool the fundamental propertiesunderlying the theory of Network Calculus. These results involverelatively basic properties on real numbers, such as upper bounds oreven limits of piecewise linear functions. We use the Coqproof assistant as well as the Mathematical components library.Effective computations rely on operators from the min-plus algebra onreal functions. Algorithms on specific subsets can be found in theliterature. Such algorithms and related implementations arehowever complicated. Instead of redeveloping a provably correctimplementation, we take an existing implementation as an oracle andpropose a Coq based verifier.Anne Bouillard, Marc Boyer et Euriell Le Corronc. DeterministicNetwork Calculus : From Theory to Practical Implementation. John Wiley& Sons, Ltd, oct. 2018Assia Mahboubi et Enrico Tassi. Mathematical Components. Zenodo,jan. 2021Anne Bouillard et Eric Thierry. « An Algorithmic Toolbox forNetwork Calculus ». In : Discret. Event Dyn. Syst. 18.1 (2008),p. 3-49.De nos jours les avions ne peuvent se passer d'un important rĂ©seau embarquĂ© pour faire communiquer les nombreux capteurs et actionneurs qui y sont dissĂ©minĂ©s. Ces rĂ©seaux ayant une fonction critique, en particulier pour les commandes de vol, il est important d'en garantir certaines propriĂ©tĂ©s telles des dĂ©lais de traversĂ©e ou l'absence de dĂ©bordement de buffers. Le calcul rĂ©seau est une mĂ©thode mathĂ©matique permettant de rĂ©aliser de telles preuves [2]. Elle a jouĂ© un rĂŽle clef dans la certification du rĂ©seau AFDX, dĂ©rivĂ© de l'ethernet, utilisĂ© Ă bord des avions les plus rĂ©cents (A380, A350).Le Calcul RĂ©seau se base sur des rĂ©sultats mathĂ©matiques utilisant l'algĂšbre tropicale. Ces rĂ©sultats sont relativement simple mais dĂ©jĂ bien assez subtiles pour qu'il soit trĂšs facile de commettre des erreurs ou des omissions lors de preuves papier ou de calcul de valeur concrĂštes. Par ailleurs, les assistants de preuve sont un bon outil pour rĂ©aliser une vĂ©rification mĂ©canique de ce genre de preuves et obtenir un trĂšs haut niveau de confiance dans leurs rĂ©sultats. Nous formalisons donc avec un tel outil les notions et propriĂ©tĂ©s fondamentales de la thĂ©orie du Calcul RĂ©seau. Ces rĂ©sultats font intervenir des propriĂ©tĂ©s sur les nombres rĂ©els, tel que des bornes supĂ©rieures et des limites de fonctions linĂ©aires donc nous souhaitons utiliser un outil de formalisation capable d'implĂ©menter untel niveau mathĂ©matique. Nous utilisons l'assistant de preuve Coq. Il s'agit d'un outil disposant dĂ©jĂ d'un long dĂ©veloppement dont la librairie Mathematical Components qui permet de formaliser de l'analyse sur les nombres rĂ©els et la construction de structures algĂ©briques comme celles utilisĂ©es dans le Calcul RĂ©seau. Le calcul de valeurs effective repose sur des opĂ©rations de l'algĂšbre min-plus sur des fonctions rĂ©elles. Des algorithmes sur des sous-ensembles spĂ©cifiques peuvent ĂȘtre trouvĂ©s dans la littĂ©rature [3]. De tels algorithmes et leurs implĂ©mentations sont toutefois compliquĂ©s. PlutĂŽt que de dĂ©velopper une preuve de la bonne implĂ©mentation de ces algorithmes, nous prenons une implĂ©mentation existante comme Oracle et nous donnons des critĂšres de vĂ©rifications en Coq.[1] Anne Bouillard, Marc Boyer et Euriell Le Corronc. DeterministicNetwork Calculus : From Theory to Practical Implementation. John Wiley& Sons, Ltd, oct. 2018[2] Assia Mahboubi et Enrico Tassi. Mathematical Components. Zenodo,jan. 2021[3] Anne Bouillard et Eric Thierry. « An Algorithmic Toolbox forNetwork Calculus ». In : Discret. Event Dyn. Syst. 18.1 (2008),p. 3-49
Vérification formelle de réseaux temps réel
International audienceEmbedded real-time networks must ensure guaranteed delays. Network calculus is a theory providing bounds on such delays. This mathematical theory currently relies on, human made, pen and paper proofs. The current work offers to formalize such proofs in Coq, an automated proof checker. We formalize a subset of the theory large enough to handle a complete proof of bounds on a representative case study
Landâuse intensification increases richness of native and exotic herbaceous plants, but not endemics, in Malagasy vanilla landscapes
Abstract
Aim
Northâeastern Madagascar is a hotspot of plant diversity, but vanilla and rice farming are driving landâuse change, including slashâandâburn management. It still remains unknown how landâuse change and landâuse history affect richness and composition of endemic, native and exotic herbaceous plant species.
Location
Northâeastern Madagascar.
Methods
We assessed herbaceous plants along a landâuse intensification gradient ranging from unburned landâuse types (i.e. oldâgrowth forest, forest fragment and forestâderived vanilla agroforest) to burned landâuse types (i.e. fallowâderived vanilla agroforest, woody fallow and herbaceous fallow) and rice paddy. We compared landâuse types and analysed the effects of landâuse history, canopy closure and landscape forest cover on species richness. Additionally, we analysed species compositional changes across landâuse types.
Results
Across 80 plots, we found 355 plant species (180 native nonâendemics, 57 exotics, 60 endemics and 58 species of unknown origin). Native and exotic species richness increased with increasing landâuse intensity, whereas endemics decreased. Unburned landâuse types had higher endemic species richness (4.28 ± 0.37 [mean ± SE]) than burned ones (2.4 ± 0.21). Exotic and native species richness, but not endemics, decreased with increasing canopy closure. Increasing landscape forest cover reduced exotic, but not native or endemic richness. Species composition of oldâgrowth forests was unique compared to all other land uses and forestâderived, not fallowâderived vanilla agroforests, had a similar endemic species composition to forest fragments.
Main conclusions
Our results indicate that oldâgrowth forests and forest fragments are indispensable for maintaining endemic herbaceous plants. We further show that the landâuse history of agroforests should be considered in conservation policy. In forestâderived vanilla agroforests, management incentives are needed to halt loss of canopy closure, thereby maintaining or even enhancing endemics. In conclusion, considering species origin (endemic, native and exotic) and composition is essential for the identification of suitable management practices to avoid irreversible species loss
High Seroprevalence of IgG Antibodies to Multiple Arboviruses in People Living with HIV (PLWHIV) in Madagascar
To estimate the prevalence of IgG antibodies against six arboviruses in people living with HIV-1 (PLWHIV) in Madagascar, we tested samples collected between January 2018 and June 2021. We used a Luminex-based serological assay to detect IgG antibodies against antigens from Dengue virus serotypes 1â4 (DENV1â4), Zika virus (ZIKV), West Nile virus (WNV), Usutu virus (USUV), Chikungunya virus (CHIKV), and Oânyong nyong virus (ONNV). Of the 1036 samples tested, IgG antibody prevalence was highest for ONNV (28.4%), CHIKV (26.7%), WNV-NS1 (27.1%), DENV1 (12.4%), USUV (9.9%), and DENV3 (8.9%). ZIKV (4.9%), DENV2 (4.6%), WNV-D3 (5.1%), and DENV4 (1.4%) were lower. These rates varied by province of origin, with the highest rates observed in Toamasina, on the eastern coast (50.5% and 56.8%, for CHIKV and ONNV, respectively). The seroprevalence increased with age for DENV1 and 3 (p = 0.006 and 0.038, respectively) and WNV DIII (p = 0.041). The prevalence of IgG antibodies against any given arborvirus varied over the year and significantly correlated with rainfalls in the different areas (r = 0.61, p = 0.036). Finally, we found a significant correlation between the seroprevalence of antibodies against CHIKV and ONNV and the HIV-1 RNA plasma viral load. Thus, PLWHIV in Madagascar are highly exposed to various arboviruses. Further studies are needed to explain some of our findings