State constrained reachability for stochastic hybrid systems

The stochastic hybrid systems constitute well established classes of realistic models of hybrid discrete/continuous dynamics subject to random perturbations, autonomous uncontrollable transitions, nondeterminism or uncertainty. Stochastic reachability analysis is a key factor in the verification and deployment of stochastic hybrid systems. The encouraging recent progress prompts us to rene the problem to cover more realistic situations. We extend the so called constrained reachability problem from the probabilistic discrete case to stochastic hybrid systems. Then we dene mathematically this problem, and we obtain the reach probabilities as solutions of a boundary value problem. The last problem is well studied and numerical, even symbolic solutions exist. This characterization is useful in stochastic control, in probabilistic path planning and for nano-systems

Dealing with stochastic reachability

For stochastic hybrid systems, stochastic reachability is very little supported mainly because of complexity and difficulty of the associated mathematical problems. In this paper, we develop two main directions of studying stochastic reachability as an optimal stopping problem. The first approach studies the hypotheses for the dynamic programming corresponding with the optimal stopping problem for stochastic hybrid systems. In the second approach, we investigate the reachability problem considering approximations of stochastic hybrid systems. The main difficulty arises when we have to prove the convergence of the value functions of the approximating processes to the value function of the initial process. An original proof is provided

Workshop on Formal Methods for Aerospace (FMA)

The coexistence of multiple disciplinary perspectives on the same class of critical applications (aerospace) and investigation (formal) methods leads naturally to the opportunity to define multidisciplinary approaches. Thus, work in this area will likely underline the importance of some research problems from aerospace to the formal methods community, and promote new formal techniques combining the principles of artificial intelligence and control engineering. The source of new problems for formal methods comes from the great diversity of aerospace systems. These can be satellites, unmanned aerial vehicles (UAVs), terrestrial or other kinds of flying robots. These systems can be involved in complex activities such as space exploration, telecommunication support, fire detection, geo-mapping, weather prognoses, geo-rectification, search and rescue, naval traffic surveillance, tracking high value targets. From these applications, new research problems appear: autonomy, collective behaviour, information fusion, cognitive skills, coordination, flocking, etc. In addition, new concepts must be formalised: digital pheromones, swarms, system of systems of robots, sensing, physical actuation, and so on. Aerospace systems are not only safety critical, but also mission critical and have very high performance requirements. For example, there is no safety issue regarding a planetary rover, but the system performance must justify the great cost of deploying it. Consequently, aerospace enriches traditional formal methods topics with new (or, at least, rarely investigated) research issues. Formal methods could greatly benefit from integration with approaches from other disciplines, and many such opportunities are now appearing. A good example is the problem of coordination for platoons of UAVs or satellites, which have been successfully, tackled using various techniques from control engineering and numerical tools from dynamic programming. In addition, there exist an abundance of examples artificial intelligence techniques in aerospace (target tracking, rover planning, multi-agent technologies and so on). The implementation of these methods could benefit from formal development. From the cross-fertilization of related multidisciplinary approaches, we expect more robust, safe and mechanizable development and verification methods for aerospace systems

Interdisciplinary Modeling of Autonomous Systems Deployed in Uncertain Dynamic Environments

The autonomous systems that operate in physical, random and highly dynamical environments involve a large amount of computation, which depends on the number of parameters. We tackle the problem of complexity reduction for these systems based on an interdisciplinary and qualitative approach. We define concepts like qualitative model reduction and adaptive bismulation, and use them to investigate the stochastic model checking. These concepts prove to be very useful in capturing the co-evolution between system and its environment. Potential applications in renewable energies are discussed

Bisimulation for general stochastic hybrid systems

In this paper we define a bisimulation concept for some very general models for stochastic hybrid systems (general stochastic hybrid systems). The definition of bisimulation builds on the ideas of Edalat and of Larsen and Skou and of Joyal, Nielsen and Winskel. The main result is that this bisimulation for GSHS is indeed an equivalence relation. The secondary result is that this bisimulation relation for the stochastic hybrid system models used in this paper implies the same kind of bisimulation for their continuous parts and respectively for their jumping structures

Pepetela: O cronista pós-comunista do MPLA

Quando se discute a literatura contemporânea oriunda de África, a abordagem mais comum, desde os anos 80 e particularmente nos meios académicos ocidentais, é fornecida pelos estudos pós-coloniais. Dada a história do continente, tal abordagem não pode ser surpreendente. Mas também corre o risco de generalizar literaturas específicas, negligenciando as diferenças entre experiências bem distintas. Patrick Chabal [data?] , autor do volume seminal para um entendimento da trajetória seguida pela escrita pós-independência nas antigas colónias portuguesas no continente africano – The Post-colonial Literature of Lusophone Africa – questiona repetidamente os pressupostos subjacentes a comparações baseadas na antiga língua colonial. Essencialmente, Chabal questiona a produtividade da própria categoria «lusófona», que dá título ao seu livro de 1996. Na verdade, depois de o publicar, Chabal começa a defender, mais veementemente, que as relações inter-regionais são frequentemente pontos de comparação mais apropriados. As literaturas de Moçambique e da África do Sul, por exemplo, podem oferecer pontos de comparação mais frutíferos entre si, do que com as literaturas de Angola e Cabo Verde. Para Chabal, enquanto estudiosos das literaturas de Angola, Moçambique, Cabo Verde, São Tomé e Príncipe e Guiné-Bissau, até devemos ser cautelosos quando falamos de uma «literatura pós-colonial da África lusófona» como se esta fosse uma entidade única e distinta. Em retrospectiva, «literaturas pós-coloniais» teria sido um título mais apropriado para o seu volume de 1996