Computing Distances between Probabilistic Automata

We present relaxed notions of simulation and bisimulation on Probabilistic Automata (PA), that allow some error epsilon. When epsilon is zero we retrieve the usual notions of bisimulation and simulation on PAs. We give logical characterisations of these notions by choosing suitable logics which differ from the elementary ones, L with negation and L without negation, by the modal operator. Using flow networks, we show how to compute the relations in PTIME. This allows the definition of an efficiently computable non-discounted distance between the states of a PA. A natural modification of this distance is introduced, to obtain a discounted distance, which weakens the influence of long term transitions. We compare our notions of distance to others previously defined and illustrate our approach on various examples. We also show that our distance is not expansive with respect to process algebra operators. Although L without negation is a suitable logic to characterise epsilon-(bi)simulation on deterministic PAs, it is not for general PAs; interestingly, we prove that it does characterise weaker notions, called a priori epsilon-(bi)simulation, which we prove to be NP-difficult to decide.Comment: In Proceedings QAPL 2011, arXiv:1107.074

Task-Structured Probabilistic I/O Automata

Modeling frameworks such as Probabilistic I/O Automata (PIOA) andMarkov Decision Processes permit both probabilistic andnondeterministic choices. In order to use such frameworks to express claims about probabilities of events, one needs mechanisms for resolving nondeterministic choices. For PIOAs, nondeterministic choices have traditionally been resolved by schedulers that have perfect information about the past execution. However, such schedulers are too powerful for certain settings, such as cryptographic protocol analysis, where information must sometimes be hidden. Here, we propose a new, less powerful nondeterminism-resolutionmechanism for PIOAs, consisting of tasks and local schedulers.Tasks are equivalence classes of system actions that are scheduled byoblivious, global task sequences. Local schedulers resolve nondeterminism within system components, based on local information only. The resulting task-PIOA framework yields simple notions of external behavior and implementation, and supports simple compositionality results.We also define a new kind of simulation relation, and show it to besound for proving implementation. We illustrate the potential of the task-PIOA framework by outlining its use in verifying an Oblivious Transfer protocol

Task-Structured Probabilistic I/O Automata

In the Probabilistic I/O Automata (PIOA) framework, nondeterministicchoices are resolved using perfect-information schedulers,which are similar to history-dependent policies for Markov decision processes(MDPs). These schedulers are too powerful in the setting of securityanalysis, leading to unrealistic adversarial behaviors. Therefore, weintroduce in this paper a novel mechanism of task partitions for PIOAs.This allows us to define partial-information adversaries in a systematicmanner, namely, via sequences of tasks.The resulting task-PIOA framework comes with simple notions of externalbehavior and implementation, and supports simple compositionalityresults. A new type of simulation relation is defined and proven soundwith respect to our notion of implementation. To illustrate the potentialof this framework, we summarize our verification of an ObliviousTransfer protocol, where we combine formal and computational analyses.Finally, we present an extension with extra expressive power, usinglocal schedulers of individual components

Task-Structured Probabilistic I/O Automata

"May 28, 2009."Modeling frameworks such as Probabilistic I/O Automata (PIOA) and Markov Decision Processes permit both probabilistic and nondeterministic choices. In order to use these frameworks to express claims about probabilities of events, one needs mechanisms for resolving nondeterministic choices. For PIOAs, nondeterministic choices have traditionally been resolved by schedulers that have perfect information about the past execution. However, these schedulers are too powerful for certain settings, such as cryptographic protocol analysis, where information must sometimes be hidden. Here, we propose a new, less powerful nondeterminism-resolution mechanism for PIOAs, consisting of tasks and local schedulers. Tasks are equivalence classes of system actions that are scheduled by oblivious, global task sequences. Local schedulers resolve nondeterminism within system components, based on local information only. The resulting task-PIOA framework yields simple notions of external behavior and implementation, and supports simple compositionality results. We also define a new kind of simulation relation, and show it to be sound for proving implementation. We illustrate the potential of the task-PIOAframework by outlining its use in verifying an Oblivious Transfer protocol

World Automata: a compositional approach to model implicit communication in hierarchical Hybrid Systems

We propose an extension of Hybrid I/O Automata (HIOAs) to model agent systems and their implicit communication through perturbation of the environment, like localization of objects or radio signals diffusion and detection. The new object, called World Automaton (WA), is built in such a way to preserve as much as possible of the compositional properties of HIOAs and its underlying theory. From the formal point of view we enrich classical HIOAs with a set of world variables whose values are functions both of time and space. World variables are treated similarly to local variables of HIOAs, except in parallel composition, where the perturbations produced by world variables are summed. In such way, we obtain a structure able to model both agents and environments, thus inducing a hierarchy in the model and leading to the introduction of a new operator. Indeed this operator, called inplacement, is needed to represent the possibility of an object (WA) of living inside another object/environment (WA)

Modelling Implicit Communication in Multi-Agent Systems with Hybrid Input/Output Automata

We propose an extension of Hybrid I/O Automata (HIOAs) to model agent systems and their implicit communication through perturbation of the environment, like localization of objects or radio signals diffusion and detection. To this end we decided to specialize some variables of the HIOAs whose values are functions both of time and space. We call them world variables. Basically they are treated similarly to the other variables of HIOAs, but they have the function of representing the interaction of each automaton with the surrounding environment, hence they can be output, input or internal variables. Since these special variables have the role of simulating implicit communication, their dynamics are specified both in time and space, because they model the perturbations induced by the agent to the environment, and the perturbations of the environment as perceived by the agent. Parallel composition of world variables is slightly different from parallel composition of the other variables, since their signals are summed. The theory is illustrated through a simple example of agents systems

Modeling and verification of randomized distributed real-time systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 267-274) and index.by Roberto Segala.Ph.D

Structure of a Semideciduous Seasonal Forest in the National Forest of Ipanema, Brazil: Contributing to the Floristic Knowledge of a Poorly Studied Protected Area

Studies on composition and structure generate crucial information for characterizing plant communities and planning conservation actions. There are still substantial knowledge gaps in Brazilian protected areas, preventing design programs to mitigate biodiversity loss. This is the case of the National Forest of Ipanema (Ipanema NAFO) in São Paulo state, Brazil, where plant diversity remains uncalculated. To help fill this gap, in 1-ha of a seasonal semideciduous forest (SSF) stand on the Araçoiaba hill, the authors sampled all woody stems with dbh ≥ 5 cm in a total of 103 dead and 1,301 living plants representing 65 species, 57 genera, and 31 families. The number of species and families was lower than old-growth SSF and, together with the land-use history, which suggests the community is a secondary stand. The initial species Guazuma ulmifolia, Machaerium stipitatum, Croton floribundus, and Aloysia virgata totalized 50% of the living stems, whereas 37% of the other species summed up only 1.8%. The high abundance of these initial species and the presence of the climax species Cariniana legalis, Holocayx balansae, Myroxylon peruiferum, Zanthoxylum caribaeum and others indicate that the community is in an intermediate to advanced successional stage. Three species are considered vulnerable to extinction and 27 of least concern. Ipanema NAFO is an important conservation unit, sheltering some plants vulnerable to extinction and others locally rare. This study adds to other few studies about the flora of Ipanema NAFO, helping to estimate its biodiversity and planning conservation actions. Additionally, it is a source for defining reference values for ecological restoration in the Atlantic forest

Sistematização das informações oriundas dos usuários de habitação social

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Arquitetura e Urbanismo, Florianópolis, 2016.Quando se trata da habitação social no Brasil, um tema abordado é a qualidade dos espaços de uso privativo contemplados nos projetos de arquitetura. A qualidade da habitação relaciona-se à qualidade da solução do projeto e este, por sua vez, à qualidade das informações oriundas dos usuários finais da habitação. A quase inexistência do contato direto do projetista com os usuários do chamado ?segmento econômico?, renda até 10 salários mínimos, resulta na baixa qualidade das informações que devem subsidiar as decisões de projeto. O Programa Habitacional Minha Casa Minha Vida ? PMCMV através dos procedimentos operacionais adotados pela Caixa Econômica Federal, apresenta lacuna neste processo, caracterizada por não considerar as informações oriundas dos usuários finais de forma adequada. A hipótese aqui posta considera que não há instrumento adequado à busca de informações acerca das preferências dos potenciais usuários finais sobre os espaços da habitação voltada ao segmento econômico, que subsidiem a tomada de decisão do projetista. Buscou-se no referencial teórico entendimento sobre os conceitos de habitação, qualidade habitacional e de projeto, sistemas de avaliação habitacional, percepção e preferência dos usuários. Com o objetivo de resolver esta lacuna, propõe-se demonstrar a sistematização e tratamento das informações oriundas dos usuários de habitação social, para atender a um formato de requisito para projeto. Identificou-se a relevância dos critérios a serem considerados nesta tese para a referida sistematização: Categoria I ? relativa à história habitacional dos usuários. Destaca-se o perfil do responsável pela família, a origem e procedência da família, o tempo de permanência em moradias anteriores, a composição e ciclo de vida familiar. Categoria II ? relativa às ambições e demandas vinculadas aos atributos dos espaços de uso privativo da habitação. Destaca-se a disponibilidade de cômodos e tipologia, o conforto ambiental, a flexibilidade e funcionalidade, a conservação dos materiais e acabamentos, a usabilidade do espaço exterior privado e a expectativa futura da família. Após estudo exploratório na região metropolitana de Florianópolis, atendendo à delimitação prescrita no PMCMV, obteve-se como resultado um banco de informações sistematizadas utilizando-se o software Excel. Isto permite o cruzamento das informações, o que viabiliza novos requisitos de projeto a partir da livre análise do projetista. A contribuição se dá através do avanço do conhecimento na sistematização das informações, na melhoria dos requisitos de projeto, na redução do distanciamento entre projetista e usuário final de habitação social.Abstract : When approaching social housing in Brazil, quality of private spaces embrasses architectural designs. Housing quality relates to the design solution and, in turn, to the incoming quality information from their prospective end users. The almost inexistence direct contact between the designer and the so-called users \"economic segment\", whose income are up to 10 minimum wages, results in the poor information quality that should subsidize the design decisions. The Housing Program Minha Casa Minha Vida ? PMCMV through the operational procedures adopted by Caixa Econômica Federal, presents a shortcoming in this process, characterized by not considering the information coming from the end users in an appropriate way. Here, the hypothesis considers the inadequate instrument searching for information about the potential end users preferences on the dwelling spaces looking for the economic segment, that enable the designer decision making. The theoretical concepts of housing understanding, housing and design quality, housing evaluation systems, perception, and preference of users were sought in the Literature Revue. The proposed Method is to appease this gap by demonstrating social housing users from the systematization and treatment information that lead to meet a design requirement. In doing so, the profile of the person in charge of the family, the family origin and from where they come, the length of stay in previous dwellings, the composition and family life cycle are highlighted. usystematization it was identified the criteria relevance to be considered in this research: Category I: relative to the users housing history. In doing so, the profile of the person in charge of the family, the family origin and from where they come, the length of stay in previous dwellings, the composition and family life cycle are highlighted. Category II ? related to the ambitions and demands related to the attributes of the dwelling spaces of private use. The availability of rooms and typology, environmental comfort, flexibility, and functionality, the materials and finishes shape, the usability of private outdoor space and the family's future expectations. After an exploratory study in the Metropolitan Region of Florianópolis (State of Santa Catarina), taking into account the delimitation prescribed in the PMCMV, a systematized information users? data bank was obtained, using Excel software. This allows the information crossing, which makes possible new design requirements based on the designer free analysis. The contribution is made through the advancement of systematization information knowledge, in the improvement of the design requirements, in the reduction of the distance between designer and end user of social housing

Recent Results on Computable and Compositional Semantics for Hybrid Systems

Hybrid systems combine discrete and continuous behaviors and are prevalent in applications such as automotive, robotics, and avionics, where precise interaction between control logic and dynamic environments is critical. This paper summarizes the results of [1], where a computable and compositional semantics for hybrid systems was first proposed. The formalism supports the composition of smaller subsystems and enables algorithmic analysis using computable functions. The approach addresses the challenge of undecidability in hybrid system reachability by employing approximate decision procedures. A key feature is the use of multifunctions to handle nondeterministic systems and ensure computability is preserved during system composition and the introduction of atomic interfaces to avoid circular dependencies in the composition. Several classes of computable multifunctions are identified to guarantee computational feasibility. This framework provides a scalable, compositional approach to the modeling and verification of complex hybrid systems