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Valaškevičius, Šarūnas. "Simulation tool for hybrid process algebras." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100615_084732-33186.
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A hybrid system is a system that presents both continuous time evolution and discrete events. To define and analyse such systems prior to building actual products, a hybrid process algebra can be employed. Simulation is often used as a convenient way for a better understanding of the systems’ evolution and its potential weaknesses.
This study aims at creating a general architecture of the simulation tool for hybrid process algebras, together with a practical implementation of Behavioural Hybrid Process Calculus simulator. For achieving this objective, a list of tasks has been composed, including the analysis of several hybrid process algebra operators, development of an easily extendible architecture of the tool, the definition of the input language, capable of describing BHPC processes, and a programming solution of the simulator.
Together with a simulator tool, a programming solution for the visualisation of hybrid systems’ evolution is created and presented. The application uses Message Sequence Plots diagrams to represent such evolution, which allows a convenient overview and analysis for most of hybrid system simulations.
The currently developed simulation and visualisation tools may be regarded as a working ground for both the usage and further development. The improvement points of the tools should be constantly collected from the user experience and implemented. The long term goal of the work is to achieve an expanding community with the joint effort to create a... [to full text]Hibridinė sistema yra sistema, sudaryta iš laike tolydžios evoliucijos ir diskrečių įvykių. Hibridinių procesų algebros pagalba tokias sistemas galima apibrėžti ir analizuoti dar prieš sukuriant galutinį produktą. Tuo tarpu simuliacija yra dažnai naudojama kaip patogus būdas geresniam sistemos evoliucijos suvokimui ir jos potencialių silpnybių identifikavimui. Šiuo darbu siekiama sukurti bendrą architektūrą hibridinių procesų algebrų simuliavimo įrankiui bei sukurti praktinę priemonę – simuliatorių, skirtą Elgsenos Hibridinių Procesų Algebrai (angl. Behavioural Hybrid Process Calculus – BHPC). Siekiant įgyvendinti šį tikslą, buvo sudarytas užduočių sąrašas, įtraukiant į jį kelių hibridinių procesų algebrų operatorių analizę, nesudėtingai plečiamos programos architektūros sukūrimą, įvedimo kalbos, gebančios aprašyti BHPC procesus, apibrėžimą bei programinio simuliatoriaus sprendimo įgyvendinimą. Hibridinių sistemų evoliucijos vaizdavimui buvo sukurtas programinis sprendimas, naudojantis Pranešimų Sekos Grafiko (angl. Message Sequence Plots) vaizdavimo tipą grafiniam hibridinės evoliucijos atvaizdavimui, kuris suteikia galimybę patogiai apžvelgti ir analizuoti daugumą hibridinių sistemų evoliucijų. Šiuo metu sukurti simuliavimo ir vaizdavimo įrankiai gali būti naudojami praktikoje, tuo pačiu renkant vartotojų patirtį tolesniam jų tobulinimui. Įrankių tobulinimo aspektai turėtų būti nuolatos kaupiami ir įgyvendinami siekiant ilgalaikio šio darbo tikslo – suburti augančią... [toliau žr. visą tekstą]
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Aceto, Luca. "Action refinement in process algebras /." Cambridge ; New York, NY, USA : Cambridge University Press, 1992. http://www.loc.gov/catdir/toc/cam029/92249890.html.
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Christensen, Søren. "Decidability and decomposition in process algebras." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/410.
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This thesis is concerned with the question of obtaining decidable theories for behavioural equivalences on various models of (parallel) computation encompassing systems with infinitely many states. The models on which we concentrate are based on the process calculi BPA and BPP but we also consider labelled Petri nets. The equivalences which we are interested in are language equivalence, bisimulation equivalence and distributed bisimulation equivalence. BPA (Basic Process Algebra) is provided by a standard calculus which admits of a general sequencing operator, along with atomic actions, choice and recursion. In contrast, BPP (Basic Parallel Processes) is provided by a standard calculus which admits of a simple parallel operator (full merge), along with atomic actions, choice and recursion. From the point of view of language equivalence we show that BPA and BPP are incomparable. This result is in part obtained through a pumping lemma for BPP. We furthermore show that the class of languages generated by BPP is included in a class of languages generated by labelled Petri nets as well as contained in the class of context-sensitive languages. Next we investigate into decidability of language equivalence on language classes related to BPP and Petri nets. We then move on to bisimulation equivalence. We show that this equivalence is decidable on all of BPA, answering a question left open by Baeten, Bergstra and Klop. We also show that bisimulation equivalence is decidable on BPP and BPPr, (where BPPr is similar to BPP except for its parallel operator which allows for synchronisation). By these results we have obtained a delicate line between decidable and undecidable theories for bisimilarity; by extending BPPr, with the operator of restriction we know that bisimilarity is undecidable. By relying on Jancar's recent result on the undecidability of bisimilarity on labelled Petri nets we further narrow the gap between decidable and undecidable theories; when extending BPP with a notion of forced synchronisation we know that bisimilarity is undecidable. The decidability proofs of bisimulation equivalence on BPP and BPPr (obtained via the tableau technique) permit us further to present sound and complete equational theories for these process classes. As BPP and BPPr contain the regular processes their results may be seen as proper extensions of Milner's equational theory for regular processes. In this thesis we shall also consider the problem of decomposing a process into the parallel composition of simpler processes. A particular aspect of decomposition involves decomposing uniquely into prime processes, i.e. those processes which cannot themselves be expressed as a parallel composition of other non-trivial processes. We shall present several unique decomposition results for bisimilarity and distributed bisimilarity on BPP and BPPr as well as subclasses thereof. Finally, for distributed bisimulation equivaalence we show decidability on the process classes BPP and BPPr. Again our proofs of decidability permit us to present sound and complete equational theories. These results may be seen as extensions of Castellani's equational theories for distributed bisimilarity on the recursion-free fragments of BPP and BPPr. Also for a fragment of BPPr where general summation is replaced by guarded summation shall we present an equational theory for distributed bisimilarity. The proof of completeness relies on the unique decomposition property admitted by this equivalence on BPP.
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Bradley, Jeremy Thomas. "Towards reliable modelling with stochastic process algebras." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302166.
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Kuntz, Georg Wolfgang Matthias. "Symbolic semantics and verification of stochastic process algebras." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=97894139X.
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Stríbrná, Jitka. "Decidability and complexity of equivalences for simple process algebras." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/383.
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In this thesis I study decidability, complexity and structural properties of strong and weak bisimilarity with respect to two process algebras, Basic Process Algebras and Basic Parallel Process Algebras. The decidability of strong bisimilarity for both algebras is an established result. For the subclasses of normed BPA-processes and BPP there even exist polynomial decision procedures. The complexity of deciding strong bisimilarity for the whole class of BPP is unsatisfactory since it is not bounded by any primitive recursive function. Here we present a new approach that encodes BPP as special polynomials and expresses strong bisimulation in terms of polynomial ideals and then uses a theorem about polynomial ideals (Hilbert's Basis Theorem) and an algorithm from computer algebra (Gröbner bases) to construct a new decision procedure. For weak bisimilarity, Hirshfeld found a decision procedure for the subclasses of totally normed BPA-processes and BPP, and Esparza demonstrated a semidecision procedure for general BPP. The remaining questions are still unsolved. Here we provide some lower bounds on the computational complexity of a decision procedure that might exist. For BPP we show that the decidability problem is NP-hard (even for the class of totally normed BPP), for BPA-processes we show that the decidability problem is PSPACE-hard. Finally we study the notion of weak bisimilarity in terms of its inductive definition. We start from the relation containing all pairs of processes and then form a non-increasing chain of relations by eliminating pairs that do not satisfy a certain expansion condition. These relations are labelled by ordinal numbers and are called approximants. We know that this chain eventually converges for some a' such that =a' = =b' = = for all a' < b'. We study the upper and lower bounds on such ordinals a'. We prove that for BPA, a' => w w, and for BPPA, a' => w.2. For some restricted classes of BPA and BPPA we show that = = =w.2.
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Cattani, Stefano. "Trace-based process algebras for real-time probabilistic systems." Thesis, University of Birmingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419694.
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Sangiorgi, Davide. "Expressing mobility in process algebras : first-order and higher-order paradigms." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/6569.
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We study mobile systems, i.e. systems with a dynamically changing communication topology, from a process algebras point of view. Mobility can be introduced in process algebras by allowing names or terms to be transmitted. We distinguish these two approaches as first-order and higher-order. The major target of the thesis is the comparison between them. The prototypical calculus in the first-order paradigm is the π-calculus. By generalising its sort discipline we derive an w-order extension called Higher-Order π-calculus (HOπ). We show that such an extension does not add expressiveness to the π-calculus: Higher-order processes can be faithfully compiled down to first-order, and respecting the behavioural equivalence we adopted in the calculi. Such an equivalence is based on the notion of bisimulation, a fundamental concept of process algebras. Unfortunately, the standard definition of bisimulation is unsatisfactory in a higher-order calculus because it is over-discriminating. To overcome the problem, we propose barbed bisimulation. Its advantage is that it can be defined uniformly in different calculi because it only requires that the calculus possesses an interaction or reduction relation. As a test for barbed bisimulation, we show that in CCS and π-calculus, it allows us to recover the familiar bisimulation-based equivalences. We also give simpler characterisations of the equivalences utilised in HOπ. For this we exploit a special kind of agents called triggers, with which it is possible to reason fairly efficiently in a higher-order calculus notwithstanding the complexity of its transitions. Finally, we use the compilation from HOπ to π-calculus to investigate Milner's
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Milios, Dimitrios. "On approximating the stochastic behaviour of Markovian process algebra models." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8930.
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Markov chains offer a rigorous mathematical framework to describe systems that exhibit stochastic behaviour, as they are supported by a plethora of methodologies to analyse their properties. Stochastic process algebras are high-level formalisms, where systems are represented as collections of interacting components. This compositional approach to modelling allows us to describe complex Markov chains using a compact high-level specification. There is an increasing need to investigate the properties of complex systems, not only in the field of computer science, but also in computational biology. To explore the stochastic properties of large Markov chains is a demanding task in terms of computational resources. Approximating the stochastic properties can be an effective way to deal with the complexity of large models. In this thesis, we investigate methodologies to approximate the stochastic behaviour of Markovian process algebra models. The discussion revolves around two main topics: approximate state-space aggregation and stochastic simulation. Although these topics are different in nature, they are both motivated by the need to efficiently handle complex systems. Approximate Markov chain aggregation constitutes the formulation of a smaller Markov chain that approximates the behaviour of the original model. The principal hypothesis is that states that can be characterised as equivalent can be adequately represented as a single state. We discuss different notions of approximate state equivalence, and how each of these can be used as a criterion to partition the state-space accordingly. Nevertheless, approximate aggregation methods typically require an explicit representation of the transition matrix, a fact that renders them impractical for large models. We propose a compositional approach to aggregation, as a means to efficiently approximate complex Markov models that are defined in a process algebra specification, PEPA in particular. Regarding our contributions to Markov chain simulation, we propose an accelerated method that can be characterised as almost exact, in the sense that it can be arbitrarily precise. We discuss how it is possible to sample from the trajectory space rather than the transition space. This approach requires fewer random samples than a typical simulation algorithm. Most importantly, our approach does not rely on particular assumptions with respect to the model properties, in contrast to otherwise more efficient approaches.
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Prokopová, Dagmar. "Vizualizace výrazů procesní algebry pi-kalkul." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2017. http://www.nusl.cz/ntk/nusl-363857.
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This work deals with the problem of visual representation of Pi-calculus expressions. The theoretical part of this paper discusses general principles of process algebras as well as specific properties of individual models, with a focus on Pi-calculus. Also included is the comparison of several text and graphical representations of expressions. The main part of the thesis deals with the design and implementation of an application for converting text representation of expressions into graphical representation. In addition to the text and graphical representation, an internal tree representation designed to work with expressions within the application is also proposed. The thesis also describes algorithms for finding feasible reductions, performing reductions and expression simplification that operate with the proposed tree representation.
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Bartels, Björn [Verfasser], Sabine [Akademischer Betreuer] Glesner, Ernst-Rüdiger [Akademischer Betreuer] Olderog, and Stefan [Akademischer Betreuer] Jähnichen. "A mechanized verification environment for real-time process algebras and low-level programming languages / Björn Bartels. Gutachter: Sabine Glesner ; Ernst-Rüdiger Olderog ; Stefan Jähnichen. Betreuer: Sabine Glesner." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1066163103/34.
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Vekris, Dimitrios. "Vérification de spécifications EB-3 à l'aide de techniques de model-checking." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1117/document.
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EB-3 est un langage de spécification développé pour la spécification des systèmes d'information. Le noyau du langage EB-3comprend des spécifications d'algèbre de processus afin de décrire le comportement des entités du système et des fonctions d'attributs qui sont des fonctions récursives dont l'évaluation se fait sur la trace d'exécution du système décrivant les attributs des entités. La vérification de propriétés temporelles en EB-3 est un sujet de grande importance pour des utilisateurs de EB-3. Dans cette thèse, on se focalise sur les propriétés de vivacité concernant des systèmes d'information exprimant l'éventualité que certaines actions puissent s'exécuter. La vérification des propriétés de vivacité se fait à l'aide de model checking. Dans un premier temps, on présente une sémantique opérationnelle deEB-3, selon laquelle les fonctions d'attributs sont évaluées pendant l'exécution du programme puis stockées. Cette sémantique nous permet de définir une traduction automatique de EB-3 vers LNT, qui est un langage simultané enrichi d'une algèbre de processus. Notre traduction assure la correspondance un à un entre les états et les transitions des systèmes étiquetés de transition correspondent respectivement à des spécifications EB-3 et LNT. Ensuite, on automatise la traduction grâce à l'outil EB3toLNT fournissant aux utilisateurs de EB-3 une tous les outils de vérification fonctionnelle disponible dans CADP. Dans le but d'améliorer les résultats de notre approche concernant le model checking, on explore des techniques d'abstraction dédiées aux systèmes d'information spécifiées en EB-3. En particulier, on se focalise sur une famille spécifique de systèmes qui s'appellent paramétriques dont le comportement varie en fonction de la valeur prédéfinie d'un paramètre du système. Enfin, on applique cette méthode dans le contexte de EB-3EB-3 is a specification language for information systems. The core of the EB-3 language consists of process algebraic specifications describing the behaviour of entities in a system, and attribute functions that are recursive functions evaluated on the system execution trace describing entity attributes. The verification ofEB-3 specifications against temporal properties is of great interest to users of EB-3. In this thesis, we focus on liveness properties of information systems, which express the eventuality that certain actions take place. The verification of liveness properties can beachieved with model checking. First, we present an operational semantics for EB-3 programs, in which attribute functions are computed during program evolution and their values are stored into program memory. This semantics permits us to define an automatic translation from EB-3 to LNT, a value-passing concurrent language with classical process algebra features. Our translation ensures the one-to-one correspondence between states and transitions of the labelled transition systems corresponding to theEB-3 and LNT specifications. Then, we automate this translation with the EB-3toLNT tool, thus equipping the EB-3 method with the functional verification features available in the model checking toolbox CADP. With the aim of improving the model checking results of this approach, we explore abstraction techniques for information systems specified inEB-3. In particular, we concentrate on a specific family of systems called parametric, whose behaviour is scaled in keeping with the predefined value of a system parameter. Finally, we apply this method on the EB-3 context
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Briscoe-Smith, C. "Behavioural subtyping in process algebra." Thesis, University of Kent, 2000. https://kar.kent.ac.uk/21936/.
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Subtyping relations embody a notion of substitutability, and are an important tool in formal methods. The downward simulation relation is well-known and widely used as a subtyping and refinement relation for state-based approaches, but there is no single relation which is widely accepted to be the subtyping relation for the behavioural setting; however, there are several candidate relations. Developments such as the multi-viewpoint specification method of RM-ODP encourage the use of several different formal methods in a single project. Thus, it becomes important to obtain implementations of a single notion of subtyping in several different paradigms. In this thesis, we attempt to find a process algebraic relation which corresponds to the state-based subtyping relation, downward simulation. While trying to achieve this, we define a translation between a state-based notation and a process algebra, and we uncover some of the similarities and differences between these two specification paradigms. In particular, we investigate the meaning of undefined behaviour in each setting. When a state-based specification does not define an operation, the intent is that the system's behaviour is unspecified (not well-defined) if that operation is invoked. In a process algebra with refusals semantics, however, a process is implicitly specified to refuse any action it is not specified to accept, and such a refusal constitutes well-defined behaviour. As part of our translation, we devise a method of representing the unspecified behaviour of the state-based world in a process definition. Finally, we use our translation to prove that the presence of subtyping between a pair of state-based specifications implies reduction between their LOTOS translations, but that the presence of reduction does not imply subtyping. We conclude that reduction itself does not correspond to state-based subtyping, but that any relation which does must be based on a stronger semantics than reduction, such as bisimulation semantics.
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Dihego, da Silva Oliveira Jose. "Algebraic laws for process subtyping." Universidade Federal de Pernambuco, 2011. https://repositorio.ufpe.br/handle/123456789/2660.
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Previous issue date: 2011Conselho Nacional de Desenvolvimento Científico e Tecnológico
Uma abordagem formal e crucial na especificação e desenvolvimento de sistemas complexos. Inspirado pela engenharia, o desenvolvimento de software deve preterir a abordagem empirica e seguir uma abordagem estruturada, formal, passível de repetição e prova face ao advento de sistemas mais complexos, paralelos e concorrentes. Este trabalho apresenta uma extensão conservativa de OhCircus, uma linguagem de especificação oncorrente, que integra CSP, Z, orientação a objetos e um calculo de re- finamento. Esta extensão suporta a definição de heranca de processo, onde uxo de controle, operações e componentes de estado em um superprocesso, podem ser reusados por seus subprocessos. Neste trabalho nos apresentamos a gramatica estendida de OhCir- cus, acompanhada por um conjunto de regras de tipos que lidam com as novas construções da linguagem. Nos apresentamos, em termos da Unifying Theories of Programming definida por Hoare e He, a semântica formal de heranca de processo e suas construções de suporte. A principal contribuição deste trabalho e um conjunto, formalmente provado, de leis algebricas que lidam com herança de processo. Nós também explanamos informalmente como essas leis podem contribuir para uma teoria de completude para OhCircus. Finalmente nossas leis são exercitadas atraves de um estudo de caso
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Tschaikowski, Max. "Fluid aggregations for Markovian process algebra." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-171109.
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Quantitative analysis by means of discrete-state stochastic processes is hindered by the well-known phenomenon of state-space explosion, whereby the size of the state space may have an exponential growth with the number of objects in the model. When the stochastic process underlies a Markovian process algebra model, this problem may be alleviated by suitable notions of behavioural equivalence that induce lumping at the underlying continuous-time Markov chain, establishing an exact relation between a potentially much smaller aggregated chain and the original one. However, in the modelling of massively distributed computer systems, even aggregated chains may be still too large for efficient numerical analysis. Recently this problem has been addressed by fluid techniques, where the Markov chain is approximated by a system of ordinary differential equations (ODEs) whose size does not depend on the number of the objects in the model. The technique has been primarily applied in the case of massively replicated sequential processes with small local state space sizes. This thesis devises two different approaches that broaden the scope of applicability of efficient fluid approximations. Fluid lumpability applies in the case where objects are composites of simple objects, and aggregates the potentially massive, naively constructed ODE system into one whose size is independent from the number of composites in the model. Similarly to quasi and near lumpability, we introduce approximate fluid lumpability that covers ODE systems which can be aggregated after a small perturbation in the parameters. The technique of spatial aggregation, instead, applies to models whose objects perform a random walk on a two-dimensional lattice. Specifically, it is shown that the underlying ODE system, whose size is proportional to the number of the regions, converges to a system of partial differential equations of constant size as the number of regions goes to infinity. This allows for an efficient analysis of large-scale mobile models in continuous space like ad hoc networks and multi-agent systems.
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Compton, Michael James. "Formal verification of process algebra systems." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612067.
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Bohnenkamp, Henrik. "Compositional solution of stochastic process algebra models." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965593193.
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Tribastone, Mirco. "Scalable analysis of stochastic process algebra models." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4629.
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The performance modelling of large-scale systems using discrete-state approaches is fundamentally hampered by the well-known problem of state-space explosion, which causes exponential growth of the reachable state space as a function of the number of the components which constitute the model. Because they are mapped onto continuous-time Markov chains (CTMCs), models described in the stochastic process algebra PEPA are no exception. This thesis presents a deterministic continuous-state semantics of PEPA which employs ordinary differential equations (ODEs) as the underlying mathematics for the performance evaluation. This is suitable for models consisting of large numbers of replicated components, as the ODE problem size is insensitive to the actual population levels of the system under study. Furthermore, the ODE is given an interpretation as the fluid limit of a properly defined CTMC model when the initial population levels go to infinity. This framework allows the use of existing results which give error bounds to assess the quality of the differential approximation. The computation of performance indices such as throughput, utilisation, and average response time are interpreted deterministically as functions of the ODE solution and are related to corresponding reward structures in the Markovian setting. The differential interpretation of PEPA provides a framework that is conceptually analogous to established approximation methods in queueing networks based on meanvalue analysis, as both approaches aim at reducing the computational cost of the analysis by providing estimates for the expected values of the performance metrics of interest. The relationship between these two techniques is examined in more detail in a comparison between PEPA and the Layered Queueing Network (LQN) model. General patterns of translation of LQN elements into corresponding PEPA components are applied to a substantial case study of a distributed computer system. This model is analysed using stochastic simulation to gauge the soundness of the translation. Furthermore, it is subjected to a series of numerical tests to compare execution runtimes and accuracy of the PEPA differential analysis against the LQN mean-value approximation method. Finally, this thesis discusses the major elements concerning the development of a software toolkit, the PEPA Eclipse Plug-in, which offers a comprehensive modelling environment for PEPA, including modules for static analysis, explicit state-space exploration, numerical solution of the steady-state equilibrium of the Markov chain, stochastic simulation, the differential analysis approach herein presented, and a graphical framework for model editing and visualisation of performance evaluation results.
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Vu, Thuy Duong. "Semantics and applications of process and program algebra." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2007. http://dare.uva.nl/document/44054.
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Pua, Chai Seng. "Process algebra approach to parallel DBMS performance modelling." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/1262.
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Degasperi, Andrea. "Multi-scale modelling of biological systems in process algebra." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2946/.
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There is a growing interest in combining different levels of detail of biological phenomena into unique multi-scale models that represent both biochemical details and higher order structures such as cells, tissues or organs. The state of the art of multi-scale models presents a variety of approaches often tailored around specific problems and composed of a combination of mathematical techniques. As a result, these models are difficult to build, compose, compare and analyse. In this thesis we identify process algebra as an ideal formalism to multi-scale modelling of biological systems. Building on an investigation of existing process algebras, we define process algebra with hooks (PAH), designed to be a middle-out approach to multi-scale modelling. The distinctive features of PAH are: the presence of two synchronisation operators, distinguishing interactions within and between scales, and composed actions, representing events that occur at multiple scales. A stochastic semantics is provided, based on functional rates derived from kinetic laws. A parametric version of the algebra ensures that a model description is compact. This new formalism allows for: unambiguous definition of scales as processes and interactions within and between scales as actions, compositionality between scales using a novel vertical cooperation operator and compositionality within scales using a traditional cooperation operator, and relating models and their behaviour using equivalence relations that can focus on specified scales. Finally, we apply PAH to define, compose and relate models of pattern formation and tissue growth, highlighting the benefits of the approach.
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Maffeis, Sergio. "Dynamic Web data : a process algebraic approach." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436321.
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Fujinami, Tsutomu. "A process algebraic approach to computational linguistics." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/521.
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The thesis presents a way to apply process algebra to computational linguistics. We are interested in how contexts can affect or contribute to language understanding and model the phenomena as a system of communicating processes to study the interaction between them in detail. For this purpose, we turn to the pie-calculus and investigate how communicating processes may be defined. While investigating the computational grounds of communication and concurrency,we devise a graphical representation for processes to capture the structure of interaction between them. Then, we develop a logic, combinatory intuitionistic linear logic with equality relation, to specify communicating processes logically. The development enables us to study Situation Semantics with process algebra. We construct semantic objects employed in Situation Semantics in the pi-calculus and then represent them in the logic. Through the construction,we also relate Situation Semantics with the research on the information flow, Channel Theory, by conceiving of linear logic as a theory of the information flow. To show how sentences can be parsed as the result of interactions between processes, we present a concurrent chart parser encoded in the pi-calculus. We also explain how a semantic representation can be generated as a process by the parser. We conclude the thesis by comparing the framework with other approaches.
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Tian, Chun. "A formalization of unique solutions of equations in process algebra." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14798/.
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In this thesis, a comprehensive formalization of Milner's Calculus of Communicating Systems (also known as CCS) has been done in HOL theorem prover (HOL4), based on an old work in HOL88. This includes all classical properties of strong/weak bisimulation equivalences and observation congruence, a theory of congruence for CCS, various versions of ``bisimulation up to'' techniques, and several deep theorems, namely the ``coarsest congruence contained in weak equivalence'', and three versions of the ``unique solution of equations'' theorem in Milner's book.
This work is further extended to support recent developments in Concurrency Theory, namely the ``contraction'' relation and the related ``unique solutions of contractions'' theorem found by Prof. Davide Sangiorgi, University of Bologna. As a result, a rather complete theory of ``contraction'' (and a similar relation called ``expansion'') for CCS is also formalized in this thesis. Further more, a new variant of contraction called ``observational contraction'' was found by the author during this work, based on existing contraction relation. It's formally proved that, this new relation is preserved by direct sums of CCS processes, and has a more elegant form of the ``unique solutions of contractions'' theorem without any restriction on the CCS grammar.
The contribution of this thesis project is at least threefold: First, it can be seen as a formal verification of the core results in Prof.\ Sangiorgi's paper, and it provides all details for the informal proof sketches given in the paper. Second, a large piece of old proof scripts from the time of Hol88 (1990s) has been ported to HOL4 and made available to all its users. Third, it's a proof engineering research by itself on the correct formalization of process algebra, because the work has made extensive uses of some new features (e.g. coinductive relation) provided in recent versions of HOL4 (Kananaskis-11 and later).
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Kazantzi, Vasiliki. "Novel visualization and algebraic techniques for sustainable development through property integration." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4930.
Full textAbstract:
The process industries are characterized by the significant consumption of fresh
resources. This is a critical issue, which calls for an effective strategy towards more
sustainable operations. One approach that favors sustainability and resource
conservation is material recycle and/or reuse. In this regard, an integrated framework is
an essential element in sustainable development. An effective reuse strategy must
consider the process as a whole and develop plant-wide strategies. While the role of
mass and energy integration has been acknowledged as a holistic basis for sustainable
design, it is worth noting that there are many design problems that are driven by
properties or functionalities of the streams and not by their chemical constituency. In this
dissertation, the notion of componentless design, which was introduced by Shelley and
El-Halwagi in 2000, was employed to identify optimal strategies for resource
conservation, material substitution, and overall process integration.
First, the focus was given on the problem of identifying rigorous targets for material
reuse in property-based applications by introducing a new property-based pinch analysis
and visualization technique. Next, a non-iterative, property-based algebraic technique,
which aims at determining rigorous targets of the process performance in materialrecycle
networks, was developed. Further, a new property-based procedure for
determining optimal process modifications on a property cluster diagram to optimize the
allocation of process resources and minimize waste discharge was also discussed. In
addition, material substitution strategies were considered for optimizing both the process
and the fresh properties. In this direction, a new process design and molecular synthesis methodology was evolved by using the componentless property-cluster domain and
Group Contribution Methods (GCM) as key tools in developing a generic framework
and systematic approach to the problem of simultaneous process and molecular design.
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Almutlaq, Abdulaziz M. "Algebraic approaches to resource conservation via process integration." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2533.
Full textAbstract:
The primary objective of this dissertation is to introduce several algebraic
procedures to the targeting of material recycle networks. The problem involves the
allocation of process streams and fresh sources to process units (sinks) with the objective
of minimizing fresh purchase and waste discharge. In the case of composition-limited
sinks, allocation to process sinks is governed by feasibility constraints on flowrates and
compositions. A systematic non-iterative algebraic approach is developed to identify
rigorous targets for minimum usage of fresh resources, maximum recycle of process
resources and minimum discharge of waste. These targets are identified a priori and
without commitment to the detailed design of the recycle/reuse network. The approach is
valid for both pure and impure fresh resources. The devised procedures also identifies the
location of the material recycle pinch point and addresses its significance in managing
process sources, fresh usage, and waste discharge. The dissertation also addresses the
targeting of material-recycle networks when the constraints on the process units are
described through flowrates and properties. This property-integration problem is solvedusing a non-iterative cascade-based algebraic procedure. Finally, for more complex cases
with multiple fresh sources and with interception networks, a mathematical-programming
approach is developed. Because of the nonlinear non-convex characteristics of the
problem, the mathematical model is reformulated to enable the global solution of the
problem. Several case studies are solved to illustrate the ease, rigor, and applicability of
the developed targeting technique.
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Tschaikowski, Max [Verfasser], and Mirco [Akademischer Betreuer] Tribastone. "Fluid aggregations for Markovian process algebra / Max Tschaikowski. Betreuer: Mirco Tribastone." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1053618638/34.
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Scott, Erin G. "Process algebra with layers : a language for multi-scale integration modelling." Thesis, University of Stirling, 2016. http://hdl.handle.net/1893/23516.
Full textAbstract:
Multi-scale modelling and analysis is becoming increasingly important and relevant. Analysis of the emergent properties from the interactions between scales of multi-scale systems is important to aid in solutions. There is no universally adopted theoretical/computational framework or language for the construction of multi-scale models. Most modelling approaches are specific to the problem that they are addressing and use a hybrid combination of modelling languages to model specific scales. This thesis addresses if process algebra can offer a unique opportunity in the definition and analysis of multi-scale models. In this thesis the generic Process Algebra with Layers (PAL) is defined: a language for multi-scale integration modelling. This work highlights the potential of process algebra to model multi-scale systems. PAL was designed based on features and challenges found from modelling a multi-scale system in an existing process algebra. The unique features of PAL are the layers: Population and Organism. The novel language modularises the spatial scales of the system into layers, therefore, modularising the detail of each scale. An Organism can represent a molecule, organelle, cell, tissue, organ or any organism. An Organism is described by internal species. An internal species, dependent on the scale of the Organism, can also represent a molecule, organelle, cell, tissue, organ or any organism. Populations hold specific types of Organism, for example, life stages, cell phases, infectious states and many more. The Population and Organism layers are integrated through mirrored actions. This novel language allows the clear definition of scales and interactions within and between these scales in one model. PAL can be applied to define a variety of multi-scale systems. PAL has been applied to two unrelated multi-scale system case studies to highlight the advantages of the generic novel language. Firstly the effects of ocean acidification on the life stages of the Pacific oyster. Secondly the effects of DNA damage from cancer treatment on the length of a cell cycle and cell population growth.
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Cândido, Renato Markele Ferreira 1988. "Filtros de partículas aplicados a sistemas max plus." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259747.
Full textAbstract:
Orientador: Rafael Santos MendesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-24T01:12:10Z (GMT). No. of bitstreams: 1 Candido_RenatoMarkeleFerreira_M.pdf: 1921815 bytes, checksum: a5e82ec1bfadd836b1ba66fda5ce00ec (MD5) Previous issue date: 2013
Resumo: A principal contribuição desta dissertação é a proposta de algoritmos de filtragem por partículas em sistemas a eventos discretos nos quais predominam os problemas de sincronização. Esta classe de sistemas pode ser descrita por meio de equações lineares em uma álgebra não convencional usualmente conhecida como álgebra Max Plus. Os Filtros de Partículas são algoritmos Bayesianos sub-ótimos que realizam uma amostragem sequencial de Monte Carlo para construir uma aproximação discreta da densidade de probabilidade dos estados baseada em um conjunto de partículas com pesos associados. É apresentada uma revisão de sistemas a eventos discretos, de filtragem não linear e de filtros de partículas de um modo geral. Após apresentar esta base teórica, são propostos dois algoritmos de filtros de partículas aplicados a sistemas Max Plus. Em seguida algumas simulações foram apresentadas e os resultados apresentados mostraram a eficiência dos filtros desenvolvidos
Abstract: This thesis proposes, as its main contribution, particle filtering algorithms for discrete event systems in which synchronization phenomena are prevalent. This class of systems can be described by linear equation systems in a nonconventional algebra commonly known as Max Plus algebra. Particles Filters are suboptimal Bayesian algorithms that perform a sequential Monte Carlo sampling to construct a discrete approximation of the probability density of states based on a set of particles with associated weights. It is presented a review of discrete event systems, nonlinear filtering and particle filters. After presenting this theoretical background, two particle filtering algorithms applied to Max Plus systems are proposed. Finally some simulation results are presented, confirming the accuracy of the designed filters
Mestrado
Automação
Mestre em Engenharia Elétrica
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Scott, B. G. O. "A methodology for formal system development using process algebraic techniques." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294356.
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Pettersen, Jostein. "Processutveckling i praktiken : införande av processinriktat förbättringsarbete på Siemens GPMT." Thesis, Linköping University, Department of Management and Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10450.
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I en stor och komplex organisation kan det vara svårt att skapa sig en helhetsbild och se sitt arbete i relation till organisationens övergripande syfte. En sådan helhetsbild kan skapas genom att kartlägga och dokumentera aktivitetsflödet i organisationen. Processutveckling tillhandahåller verktyg för att eliminera dubbelarbete och spill och skapa bättre värde för organisationens kunder. Som resultat av detta förenklas arbetet, kostnader kan lättare reduceras och ledtider kan minskas. Allt detta sammantaget leder till ökad konkurrenskraft.
Syftet med detta examensarbete är att införa grunderna för processutveckling på Siemens GPMT. Vårt mål är att introducera och etablera ett processinriktat synsätt samt skapa verktyg för att avdelningen i framtiden själv skall kunna utveckla sin verksamhet.
Rapporten inleds med en presentation av företaget och den problembakgrund som har föranlett examensarbetet. Centrala teorier ochen allmänt applicerbar metodik för processutveckling beskrivs ingående. Slutligen presenteras de resultat vi kommit fram till under arbetets gång och en avslutande diskussion.
Vi har skapat beskrivningar av arbetet samt underlag för mätning och uppföljning av processernas prestanda. Dessutom har vi tagit fram en ledningsstruktur för fortsatt arbete med processutveckling.
Väldokumenterade processer och standardiserade arbetsrutiner är ingen garanti för goda resultat. De anger endast den befintliga kunskapsnivån som finns inom organisationen. Deras fulla potential kan endast utnyttjas om personalen verkligen tror på deras värde och arbetar för att utveckla och driva verksamheten framåt.
Vi är övertygade om att GPMT, genom att ta till sig de resonemang som vi presenterat under vårt arbete och arbetar aktivt med de metoder som vi beskrivit, kommer att utvecklas till att bli en förebild för alla andra avdelningar på Siemens.
In a large and complex organization, it is often difficult to obtain acomplete picture and be able to see individual contributions to the overall objectives of the organization.
A wide perspective can be created through mapping and documentation of the work-flow within the organization. Process management is a method containing tools that facilitates elimination of overlapping activities and waste, which leads to greater value for the customers. Through this method, work is simplified, costs can be reduced and lead-times shortened. The end result is an improved market position.
The purpose of this thesis work is to set up the fundamentals of process management at Siemens GPMT. Our goal is to introduce and establish a process oriented perspective and provide tools for the department to be able to improve their processes.
The report starts with a presentation of the company and the problembackground that has led to this thesis. Essential theories and methods for process management are thoroughly described. The results we have found under the project are presented along with a final discussion and conclusions.
We have created work descriptions along with tools for measuring and evaluating the performance of the processes. We have also created a structure for further work with process management.
Well documented processes and work standards are no guarantee for good results. They only present the current level of knowledge within the organization. Their full potential can only be utilized if the personnel really believe in their value and strive to continuously improve the business.
We are firmly convinced that GPMT, by adopting our recommendations and actively working with the methods we have described, will develop to be a role model for all other departments at Siemens.
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McCaig, Chris. "From individuals to populations : changing scale in process algebra models of biological systems." Thesis, University of Stirling, 2007. http://hdl.handle.net/1893/398.
Full textAbstract:
The problem of changing scale in models of a system is relevant in many different fields. In this thesis we investigate the problem in models of biological systems, particularly infectious disease spread and population dynamics. We investigate this problem using the process algebra \emph{Weighted Synchronous Calculus of Communicating Systems} (WSCCS). In WSCCS we can describe the different types of individual in a population and study the population by placing many of these individuals in parallel. We present an algorithm that allows us to rigorously derive mean field equations (MFE) describing the average change in the population. The algorithm takes into account the Markov chain semantics of WSCCS such that as the system being considered becomes larger, the approximation offered by the MFE tends towards the mean of the Markov chain. The traditional approach to developing population level equations of a system involves making assumptions about the behaviour of the entire population. Our approach means that the population level dynamics explained by the MFE are a direct consequence of the behaviour of individuals, which is more readily observed and measured than the behaviour of the population. In this way we develop MFE models of several different systems and compare the equations obtained to the traditional mathematical models of the system.
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Oaken, David R. "Optimisation of definition structures & parameter values in process algebra models using evolutionary computation." Thesis, University of Stirling, 2014. http://hdl.handle.net/1893/21206.
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Process Algebras are a Formal Modelling methodology which are an effective tool for defining models of complex systems, particularly those involving multiple interacting processes. However, describing such a model using Process Algebras requires expertise from both the modeller and the domain expert. Finding the correct model to describe a system can be difficult. Further more, even with the correct model, parameter tuning to allow model outputs to match experimental data can also be both difficult and time consuming. Evolutionary Algorithms provide effective methods for finding solutions to optimisation problems with large and noisy search spaces. Evolutionary Algorithms have been proven to be well suited to investigating parameter fitting problems in order to match known data or desired behaviour. It is proposed that Process Algebras and Evolutionary Algorithms have complementary strengths for developing models of complex systems. Evolutionary Algorithms require a precise and accurate fitness function to score and rank solutions. Process Algebras can be incorporated into the fitness function to provide this mathematical score. Presented in this work is the Evolving Process Algebra (EPA) framework, designed for the application of Evolutionary Algorithms (specifically Genetic Algorithms and Genetic Programming optimisation techniques) to models described in Process Algebra (specifically PEPA and Bio-PEPA) with the aim of evolving fitter models. The EPA framework is demonstrated using multiple complex systems. For PEPA this includes the dining philosophers resource allocation problem, the repressilator genetic circuit, the G-protein cellular signal regulators and two epidemiological problems: HIV and the measles virus. For Bio-PEPA the problems include a biochemical reactant-product system, a generic genetic network, a variant of the G-protein system and three epidemiological problems derived from the measles virus. Also presented is the EPA Utility Assistant program; a lightweight graphical user interface. This is designed to open the full functionality and parallelisation of the EPA framework to beginner or naive users. In addition, the assistant program aids in collating and graphing after experiments are completed.
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Vivas, Frontana Jose Luis. "Dynamic Binding of Names in Calculi for Mobile Processes." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3108.
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Hesketh, Martin. "Synthesis and axiomatisation for structural equivalences in the Petri Box Calculus." Thesis, University of Newcastle Upon Tyne, 1998. http://hdl.handle.net/10443/1993.
Full textAbstract:
The Petri Box Calculus (PBC) consists of an algebra of box expressions, and a corresponding algebra of boxes (a class of labelled Petri nets). A compo- sitional semantics provides a translation from box expressions to boxes. The synthesis problem is to provide an algorithmic translation from boxes to box expressions. The axiomatisation problem is to provide a sound and complete axiomatisation for the fragment of the calculus under consideration, which captures a particular notion of equivalence for boxes. There are several alternative ways of defining an equivalence notion for boxes, the strongest one being net isomorphism. In this thesis, the synthesis and axiomatisation problems are investigated for net semantic isomorphism, and a slightly weaker notion of equivalence, called duplication equivalence, which can still be argued to capture a very close structural similarity of con- current systems the boxes are supposed to represent. In this thesis, a structured approach to developing a synthesis algorithm is proposed, and it is shown how this may be used to provide a framework for the production of a sound and complete axiomatisation. This method is used for several different fragments of the Petri Box Calculus, and for gener- ating axiomatisations for both isomorphism and duplication equivalence. In addition, the algorithmic problems of checking equivalence of boxes and box expressions, and generating proofs of equivalence are considered as extensions to the synthesis algorithm.
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Panuška, Martin. "Business Process Modeling: A Logical Perspective." Master's thesis, Vysoká škola ekonomická v Praze, 2008. http://www.nusl.cz/ntk/nusl-19070.
Full textAbstract:
In the master's thesis we are concerned with the logical perspective on business process model-ing. The logical perspective on business process modeling has several advantages. First, being a formal logical system, first-order logic let us thoroughly understand the foundations of process modeling. Second, after we understand the logical foundations of business process modeling, we are free to build a BPM language based entirely on logic, or map an existing language onto logic, which may be useful for artificial reasoning. Third, if the business process model is mapped to logic (or another declarative language) it can be easily stored in a declarative knowledge base. Forth, logic based process models can be used in companies as a basis for knowledge manage-ment. And fifth, the science of logic offers a number of various semantic enhancements, which can be used in favor of better business process modeling expressiveness. The first objective of the thesis is to perform a thorough review of the literature of both our fields -- the business process modeling and temporal logic. The related second objective is to study the ability of logic to represent processes and the notion of time in general, and to offer techniques for logical process representation. Subsequently, the examples should be provided in order to present that the selected techniques are capable of performing what is sketched in the first paragraph. The third objective is to propose improvements of the current business process modeling approach and provide relevant examples. Eventually, means of extending the tech-niques presented can be proposed, too. The major contribution of the thesis is that it constitutes a reasonable basis for further research in the chosen field. For novices or even experienced in the subject it represents a good stepping stone.
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Guzmán, Michell. "On the expressiveness of spatial constraint systems." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX064/document.
Full textAbstract:
Les comportement épistémiques, mobiles et spatiaux sont omniprésent dans les systèmes distribués aujourd’hui. La nature intrinsèque épistémique de ces types de systèmes provient des interactions des éleménts qui en font parties. La plupart des gens sont familiarisés avec des systèmes numériques où les utilisateurs peuvent partager ses croyances, opinions et même des mensonges intentionnels (des canulars). Aussi, les modèles de ces systèmes doivent tenir compte des interactions avec d’autres de même que leur nature distribués. Ces comportements spatiaux et mobiles font part d’applications où les données se déplacent dans des espaces (peut-être imbriqués) qui sont définis par, par exemple, cercles d’amis, des groupes, ou des dossiers partagés. Nous pensons donc qu’une solide compréhension des notion d’espaces, de mobilité spatial ainsi que le flux d’information épistémique est cruciale dans la plupart des modèles de systèmes distribués de nos jours.Les systèmes de contrainte (sc) fournissent les domaines et les opérations de base pour les fondements sémantiques de la famille de modèles déclaratifs formels de la théorie de la concurrence connu sous le nom de programmation concurrent par contraintes (pcc). Les systèmes des contraintes spatiales (scs) représentent des structures algébriques qui étendent sc pour raisonner sur les comportement spatiaux et épistémiques de base tel que croyance et l’extrusion. Les assertions spatiales et épistémiques peuvent être vues comme des modalités spécifiques. D’autres modalités peuvent être utilisées pour les assertions concernant le temps, les connaissances et même pour l’analyse des groupes entre autres concepts utilisés dans la spécification et la vérification des systèmes concurrents.Dans cette thèse nous étudions l’expressivité des systèmes de contraintes spatiales dans la perspective générale du comportement modal et épistémique. Nous montrerons que les systèmes de contraintes spatiales sont assez robustes pour capturer des modalités inverses et pour obtenir de nouveaux résultats pour les logiques modales. Également, nous montrerons que nous pouvons utiliser les scs pour exprimer un comportement épistémique fondamental comme connaissance. Finalement, nous donnerons une caractérisation algébrique de la notion de l’information distribuée au moyen de constructions sur scsEpistemic, mobile and spatial behaviour are common place in today’s distributed systems. The intrinsic epistemic nature of these systems arises from the interactions of the elements taking part of them. Most people are familiar with digital systems where users share their beliefs, opinions and even intentional lies (hoaxes). Models of those systems must take into account the interactions with others as well as the distributed quality these systems present. Spatial and mobile behaviour are exhibited by applications and data moving across (possibly nested) spaces defined by, for example, friend circles, groups, and shared folders. We therefore believe that a solid understanding of the notion of space and spatial mobility as well as the flow of epistemic information is relevant in many models of today’s distributed systems.Constraint systems (cs’s) provide the basic domains and opera- tions for the semantic foundations of the family of formal declarative models from concurrency theory known as concurrent constraint programming (ccp). Spatial constraint systems (scs’s) are algebraic structures that extend cs’s for reasoning about basic spatial and epistemic behaviour such as belief and extrusion. Both spatial and epistemic assertions can be viewed as specific modalities. Other modalities can be used for assertions about time, knowledge and even the analysis of groups among other concepts used in the specification and verification of concurrent systems.In this thesis we study the expressiveness of spatial constraint systems in the broader perspective of modal and epistemic behaviour. We shall show that spatial constraint systems are sufficiently robust to capture inverse modalities and to derive new results for modal logics. We shall show that we can use scs’s to express a fundamental epistemic behaviour such as knowledge. Finally we shall give an algebraic characterization of the notion of distributed information by means of constructors over scs’s
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Bontà, Edoardo <1971>. "Automatic code generation: from process algebraic architectural descriptions to multithreaded java programs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/913/.
Full textAbstract:
Process algebraic architectural description languages provide a formal
means for modeling software systems and assessing their properties.
In order to bridge the gap between system modeling and system im-
plementation, in this thesis an approach is proposed for automatically
generating multithreaded object-oriented code from process algebraic
architectural descriptions, in a way that preserves – under certain
assumptions – the properties proved at the architectural level.
The approach is divided into three phases, which are illustrated
by means of a running example based on an audio processing
system. First, we develop an architecture-driven technique for
thread coordination management, which is completely automated
through a suitable package. Second, we address the translation
of the algebraically-specified behavior of the individual software
units into thread templates, which will have to be filled in by
the software developer according to certain guidelines. Third, we
discuss performance issues related to the suitability of synthesizing
monitors rather than threads from software unit descriptions that
satisfy specific constraints.
In addition to the running example, we present two case studies about
a video animation repainting system and the implementation of a
leader election algorithm, in order to summarize the whole approach.
The outcome of this thesis is the implementation of the proposed
approach in a translator called PADL2Java and its integration in the
architecture-centric verification tool TwoTowers.
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Siirtola, A. (Antti). "Algorithmic multiparameterised verification of safety properties:process algebraic approach." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514262524.
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Abstract
Due to increasing amount of concurrency, systems have become difficult to design and analyse. In this effort, formal verification, which means proving the correctness of a system, has turned out to be useful. Unfortunately, the application domain of the formal verification methods is often indefinite, tools are typically unavailable, and most of the techniques do not suit especially well for the verification of software systems. These are the questions addressed in the thesis.
A typical approach to modelling systems and specifications is to consider them parameterised by the restrictions of the execution environment, which results in an (infinite) family of finite-state verification tasks. The thesis introduces a novel approach to the verification of such infinite specification-system families represented as labelled transition systems (LTSs). The key idea is to exploit the algebraic properties of the correctness relation. They allow the correctness of large system instances to be derived from that of smaller ones and, in the best case, an infinite family of finite-state verification tasks to be reduced to a finite one, which can then be solved using existing tools.
The main contribution of the thesis is an algorithm that automates the reduction method. A specification and a system are given as parameterised LTSs and the allowed parameter values are encoded using first order logic. Parameters are sets and relations over these sets, which are typically used to denote, respectively, identities of replicated components and relationships between them. Because the number of parameters is not limited and they can be nested as well, one can express multiply parameterised systems with a parameterised substructure, which is an essential property from the viewpoint of modelling software systems. The algorithm terminates on all inputs, so its application domain is explicit in this sense. Other proposed parameterised verification methods do not have both these features. Moreover, some of the earlier results on the verification of parameterised systems are obtained as a special case of the results presented here.
Finally, several natural and significant extensions to the formalism are considered, and it is shown that the problem becomes undecidable in each of the cases. Therefore, the algorithm cannot be significantly extended in any direction without simultaneously restricting some other aspect.
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Benkirane, Soufiene. "Process algebra for epidemiology : evaluating and enhancing the ability of PEPA to describe biological systems." Thesis, University of Stirling, 2011. http://hdl.handle.net/1893/3603.
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Modelling is a powerful method for understanding complex systems, which works by simplifying them to their most essential components. The choice of the components is driven by the aspects studied. The tool chosen to perform this task will determine what can be modelled, the maximum number of components which can be represented, as well as the analyses which can be performed on the system. Performance Evaluation Process Algebra (PEPA) was initially developed to tackle computer systems issues. Nevertheless, it possesses some interesting properties which could be exploited for the study of epidemiological systems. PEPA's main advantage resides in its capacity to change scale: the assumptions and parameter values describe the behaviour of a single individual, while the resulting model provides information on the population behaviour. Additionally, stochasticity and continuous time have already proven to be useful features in epidemiology. While each of these features is already available in other tools, to find all three combined in a single tool is novel, and PEPA is proposed as a useful addition to the epidemiologist's toolbox. Moreover, an algorithm has been developed which allows converting a PEPA model into a system of Ordinary Differential Equations (ODEs). This provides access to countless additional software and theoretical analysis methods which enable the epidemiologist to gain further insight into the model. Finally, most existing tools require a deep understanding of the logic they are based on and the resulting model can be difficult to read and modify. PEPA's grammar, on the other hand, is easy to understand since it is based on few, yet powerful concepts. This makes it a very accessible formalism for any epidemiologist. The objective of this thesis is to determine precisely PEPA's ability to describe epidemiological systems, as well as extend the formalism when required. This involved modelling two systems: the bubonic plague in prairie dogs, and measles in England and Wales. These models were chosen as they exhibit a good range of typical features, allowing to thoroughly test PEPA. All features required in each of these models have been analysed in detail, and a solution has been provided for representing each of these features. While some of them could be expressed in a straightforward manner, PEPA did not provide the tools to express others. In those cases, we determined methods to approach the desired behaviour, and the limitations of said methods were carefully analysed. In the case of models with a structured population, PEPA was extended to simplify their expression and facilitate the writing process of the PEPA model. The work also required the development of an algorithm to derive ODEs adapted to the type of models encountered. Finally, the PEPAdum software was developed to assist the modeller in the generation and analysis of PEPA models, by simplifying the process of writing a PEPA model with compartments, performing the average of stochastic simulations and deriving and explicitly providing the ODEs using the Stirling Amendment.
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Schaeffer, Oksana. "On the use of process algebra techniques in computational modelling of cancer initiation and development." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/217/.
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Cancer research has been revolutionised by recent technological advances that allow scientists to produce extensive collections of experimental data, especially on the molecular and cellular level. Formal modelling is a necessary tool for integrating massive amounts of diverse measurement data into a coherent picture of disease development. Models can be used to test hypotheses about the role of cellular components in system function and in creating disease, and to make predictions which can then be tested experimentally. This thesis evaluates process algebra techniques as description formalisms for a collection of cancer-related models. Process algebras view biology as a dynamic interactive communication network, in which an individual agent is performing a computation corresponding to the reaction. Agents typically represent entities such as molecules or cells. The stochastic extensions of process algebras allow the modeller to assign probability (or rate) to every reaction. The analysis of the resulting models is usually based on stochastic simulation. Alternatively, formal verification tools can be used to calculate exact quantitative properties of the underlying stochastic process. We have explored the applicability of the process algebra formalism by analysing the dynamics of two cancer-related signalling pathways: Wnt/Wingless and FGF (Fibroblast Growth Factor). In addition to process algebra models, we have also derived continuous differential equation models for comparison. Systematic analysis of parameter spaces has revealed which variables have the most influence on temporal and steady state properties of the system. By integrating feedback mechanisms, amplification factors, and different time scales we have demonstrated a resulting emergence of several unexpected properties of system dynamics. We were later able to confirm these by in vitro experiments for both pathways. To examine the function of the specific signalling architecture in the cellular decision making process, we have constructed a model that couples Wnt signalling to the decision process within the cell and cell microenvironment. The model reveals signalling characteristics that ensure accuracy and robustness of Wnt-mediated determination of proliferative cell fate and lead to tissue architecture which is resistant to mutations. The main contribution of this thesis is, therefore, to systems biology; we have produced reusable and validated quantified models and demonstrated their value in designing, testing, and refining hypotheses about cancer.
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Brooke, Phillip James. "A timed semantics for a hierarchical design notation." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298382.
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Guedes, Roseliane Forgiarini. "UMA INVESTIGAÇÃO SOBRE A APRENDIZAGEM DE ÁLGEBRA POR MEIO DO USO DE JOGOS, COM ALUNOS DA 6a SÉRIE." Universidade Franciscana, 2012. http://tede.universidadefranciscana.edu.br:8080/handle/UFN-BDTD/136.
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Previous issue date: 2012-10-19Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This research aims to investigate, through the use of educational games, the algebra learning process by students of 6th grade of elementary school. The work was applied in a private school in Santa Maria, RS. The participants are students in a class of sixth grade (seventh year), seven girls and four boys, aged between 11 and 14 years. The research was developed through a qualitative approach and the class teacher was the researcher; therefore she experienced directly the relationship among students and games. Activities introductory to algebra were applied, followed by five games. The analysis was done from the field diary of the teacher researcher, through which it was possible to conclude that students felt motivated by the application of games, engaged in activities, interact with colleagues in groups and prefer this type of activity than the exercises of the book used at school. However, it is attributed to lack of time to deepen content studied, determined by the need to comply with the planning of the school, the remaining difficulties in learning of the contents. The final product takes into account this fact, in order to bring learning content in new applications of the list of activities and games.
Esta pesquisa teve como objetivo investigar, por meio do uso de jogos didáticos, a aprendizagem de conteúdos de Álgebra por alunos da 6ª série do Ensino Fundamental. O trabalho foi aplicado em uma escola particular do município de Santa Maria, RS. Os participantes são alunos de uma turma da 6ª série (7º ano), sete meninas e quatro meninos, com idades entre 11 e 14 anos. A pesquisa desenvolveu-se por meio de uma abordagem qualitativa e a professora da turma foi a pesquisadora; por conseguinte, vivenciou diretamente as relações dos alunos com os jogos aplicados. Foram aplicadas atividades introdutórias à Álgebra e, em seguida, cinco jogos. A análise dos resultados foi feita a partir do diário de campo da professora-pesquisadora, por meio do qual foi possível concluir que os alunos sentiram-se motivados com a aplicação dos jogos, envolveram-se nas atividades, interagiram com os colegas nos grupos e preferiram esse tipo de atividade a de realização dos exercícios da apostila usada na escola. No entanto, atribui-se à falta de tempo em aprofundar o conteúdo estudado, determinada pela necessidade de cumprimento do planejamento da escola, as dificuldades ainda existentes na aprendizagem dos conteúdos. O produto elaborado leva em conta esse fato, para que novas aplicações da lista de atividades e jogos possam, efetivamente, levar à aprendizagem dos conteúdos envolvidos.
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Simminger, Jerome C. "A constrained multivariable nonlinear predictive controller." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/10152.
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Vargas, Aparicio Algebra Veronica [Verfasser]. "Design of an Integrated Process Chain to Support the Manufacturing of Ti6Al4V Components / Algebra Veronica Vargas Aparicio." Aachen : Shaker, 2010. http://d-nb.info/1098041097/34.
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Feng, Cheng. "Process algebra for located Markovian agents and scalable analysis techniques for the modelling of Collective Adaptive Systems." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/22070.
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Recent advances in information and communications technology have led to a surge in the popularity of artificial Collective Adaptive Systems (CAS). Such systems, comprised by many spatially distributed autonomous entities with decentralised control, can often achieve discernible characteristics at the global level; a phenomenon sometimes termed emergence. Examples include smart transport systems, smart electricity power grids, robot swarms, etc. The design and operational management of CAS are of vital importance because different configurations of CAS may exhibit very large variability in their performance and the quality of services they offer. However, due to their complexity caused by varying degrees of behaviour, large system scale and highly distributed nature, it is often very difficult to understand and predict the behaviour of CAS under different situations. Novel modelling and quantitative analysis methodologies are therefore required to address the challenges posed by the complexity of such systems. In this thesis, we develop a process algebraic modelling formalism that can be used to express complex dynamic behaviour of CAS and provide fast and scalable analysis techniques to investigate the dynamic behaviour and support the design and operational management of such systems. The major contributions of this thesis are: (i) development of a novel high-level formalism, PALOMA, the Process Algebra for Located Markovian Agents for the modelling of CAS. CAS specified in PALOMA can be automatically translated to their underlying mathematical models called Population Continuous-Time Markov Chains (PCTMCs). (ii) development of an automatic moment-closure approximation method which can provide rapid Ordinary Differential Equation-based analysis of PALOMA models. (iii) development of an automatic model reduction algorithm for the speed up of stochastic simulation of PALOMA/PCTMC models. (iv) presenting a case study, predicting bike availability in stations of Santander Cycles, the public bike-sharing system in London, to show that our techniques are well-suited for analysing real CAS.
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Ye, Kangfeng. "Model checking of state-rich formalisms (by linking to combination of state-based formalism and process algebra)." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15526/.
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Computer-based systems are becoming more and more complex. It is really a grand challenge to assure the dependability of these systems with the growing complexity, especially for high integrity and safety critical systems that require extremely high dependability. Circus, as a formal language, is designed to tackle this problem by providing precision preservation and correctness assurance. It is a combination of Z, CSP, refinement calculus and Dijkstra's guarded commands. A main objective of Circus is to provide calculational style refinement that differentiates itself from other integrated formal methods. Looseness, which is introduced from constants and uninitialised state space in Circus, and nondeterminism, which is introduced from disjunctive operations and CSP operators, make model checking of Circus more difficult than that of sole CSP or Z. Current approaches have a number of disadvantages like nondeterminism and divergence information loss, abstraction deterioration, and no appropriate tools to support automation. In this thesis, we present a new approach to model-check state-rich formalisms by linking them to a combination of a state-based formalism and a process algebra. Specifically, the approach illustrated in this thesis is to model-check Circus by linking to CSP || B. Eventually, we can use ProB, a model checker for B, Event-B, and CSP || B etc., to check the resultant CSP || B model. A formal link from Circus to CSP || B is defined in our work. Our link solution is to rewrite Circus models first to make all interactions between the state part and the behavioural part of Circus only through schema expressions, then translate the state part and the behavioural part to B and CSP respectively. In addition, since the semantics of Circus is based on Hoare and He's Unifying Theories of Programming (UTP), in order to prove the soundness of our link, we also give UTP semantics to CSP || B. Finally, because both ends of the link have their semantics defined in UTP, they are comparable. Furthermore, in order to support an automatic translation process, a translator is developed. It has supported almost all constructs defined in the link though with some limitations. Finally, three case studies are illustrated to show the usability of our model checking solution as well as limitations. The bounded reactive buffer is a typical Circus example. By our model checking approach, basic properties like deadlock freedom and divergence freedom for both the specification and the implementation with a small buffer size have been verified. In addition, the implementation has been verified to be a refinement of the specification in terms of traces and failures. Afterwards, in the Electronic Shelf Edge Label (ESEL) case study, we demonstrate how to use Circus to model different development stages of systems from the specification to two more specific systems. We have verified basic properties and sequential refinements of three models as well as three application related properties. Similarly, only the systems with a limited number of ESELs are verified. Finally, we present the steam boiler case study. It is a real and industrial control system problem. Though our solution cannot model check the steam boiler model completely due to its large state space, our solution still proves its benefits. Through our model checking approach, we have found a substantial number of errors from the original Circus solution. Then with counterexamples during animation and model checking, we have corrected all these found errors.
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Luukkainen, Matti. "A process algebraic reduction strategy for automata theoretic verification of untimed and timed concurrent systems." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/tieto/vk/luukkainen/.
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Ding, Jie. "Structural and fluid analysis for large scale PEPA models, with applications to content adaptation systems." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/7975.
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The stochastic process algebra PEPA is a powerful modelling formalism for concurrent systems, which has enjoyed considerable success over the last decade. Such modelling can help designers by allowing aspects of a system which are not readily tested, such as protocol validity and performance, to be analysed before a system is deployed. However, model construction and analysis can be challenged by the size and complexity of large scale systems, which consist of large numbers of components and thus result in state-space explosion problems. Both structural and quantitative analysis of large scale PEPA models suffers from this problem, which has limited wider applications of the PEPA language. This thesis focuses on developing PEPA, to overcome the state-space explosion problem, and make it suitable to validate and evaluate large scale computer and communications systems, in particular a content adaption framework proposed by the Mobile VCE. In this thesis, a new representation scheme for PEPA is proposed to numerically capture the structural and timing information in a model. Through this numerical representation, we have found that there is a Place/Transition structure underlying each PEPA model. Based on this structure and the theories developed for Petri nets, some important techniques for the structural analysis of PEPA have been given. These techniques do not suffer from the state-space explosion problem. They include a new method for deriving and storing the state space and an approach to finding invariants which can be used to reason qualitatively about systems. In particular, a novel deadlock-checking algorithm has been proposed to avoid the state-space explosion problem, which can not only efficiently carry out deadlock-checking for a particular system but can tell when and how a system structure lead to deadlocks. In order to avoid the state-space explosion problem encountered in the quantitative analysis of a large scale PEPA model, a fluid approximation approach has recently been proposed, which results in a set of ordinary differential equations (ODEs) to approximate the underlying CTMC. This thesis presents an improved mapping from PEPA to ODEs based on the numerical representation scheme, which extends the class of PEPA models that can be subjected to fluid approximation. Furthermore, we have established the fundamental characteristics of the derived ODEs, such as the existence, uniqueness, boundedness and nonnegativeness of the solution. The convergence of the solution as time tends to infinity for several classes of PEPA models, has been proved under some mild conditions. For general PEPA models, the convergence is proved under a particular condition, which has been revealed to relate to some famous constants of Markov chains such as the spectral gap and the Log-Sobolev constant. This thesis has established the consistency between the fluid approximation and the underlying CTMCs for PEPA, i.e. the limit of the solution is consistent with the equilibrium probability distribution corresponding to a family of underlying density dependent CTMCs. These developments and investigations for PEPA have been applied to both qualitatively and quantitatively evaluate the large scale content adaptation system proposed by the Mobile VCE. These analyses provide an assessment of the current design and should guide the development of the system and contribute towards efficient working patterns and system optimisation.
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Skjellum, Anthony Morari Manfred. "Concurrent dynamic simulation : multicomputer algorithms research applied to ordinary differential-algebraic process systems in chemical engineering /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-11132007-090727.
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