131 research outputs found
Scalable Minimization Algorithm for Partial Bisimulation
We present an efficient algorithm for computing the partial bisimulation
preorder and equivalence for labeled transitions systems. The partial
bisimulation preorder lies between simulation and bisimulation, as only a part
of the set of actions is bisimulated, whereas the rest of the actions are
simulated. Computing quotients for simulation equivalence is more expensive
than for bisimulation equivalence, as for simulation one has to account for the
so-called little brothers, which represent classes of states that can simulate
other classes. It is known that in the absence of little brother states,
(partial bi)simulation and bisimulation coincide, but still the complexity of
existing minimization algorithms for simulation and bisimulation does not
scale. Therefore, we developed a minimization algorithm and an accompanying
tool that scales with respect to the bisimulated action subset.Comment: In Proceedings WS-FMDS 2012, arXiv:1207.184
Communicating Processes with Data for Supervisory Coordination
We employ supervisory controllers to safely coordinate high-level
discrete(-event) behavior of distributed components of complex systems.
Supervisory controllers observe discrete-event system behavior, make a decision
on allowed activities, and communicate the control signals to the involved
parties. Models of the supervisory controllers can be automatically synthesized
based on formal models of the system components and a formalization of the safe
coordination (control) requirements. Based on the obtained models, code
generation can be used to implement the supervisory controllers in software, on
a PLC, or an embedded (micro)processor. In this article, we develop a process
theory with data that supports a model-based systems engineering framework for
supervisory coordination. We employ communication to distinguish between the
different flows of information, i.e., observation and supervision, whereas we
employ data to specify the coordination requirements more compactly, and to
increase the expressivity of the framework. To illustrate the framework, we
remodel an industrial case study involving coordination of maintenance
procedures of a printing process of a high-tech Oce printer.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432
Strong, Weak and Branching Bisimulation for Transition Systems and Markov Reward Chains: A Unifying Matrix Approach
We first study labeled transition systems with explicit successful
termination. We establish the notions of strong, weak, and branching
bisimulation in terms of boolean matrix theory, introducing thus a novel and
powerful algebraic apparatus. Next we consider Markov reward chains which are
standardly presented in real matrix theory. By interpreting the obtained matrix
conditions for bisimulations in this setting, we automatically obtain the
definitions of strong, weak, and branching bisimulation for Markov reward
chains. The obtained strong and weak bisimulations are shown to coincide with
some existing notions, while the obtained branching bisimulation is new, but
its usefulness is questionable
Towards a concurrency theory for supervisory control
In this paper we propose a process-theoretic concurrency model to express supervisory control properties. In light of the present importance of reliable control software, the current work ow of direct conversion from informal specication documents to control software implementations can be improved. A separate modeling step in terms of controllable and uncontrollable behavior of the device under control is desired. We consider the control loop as a feedback model for supervisory control, in terms of the three distinct components of plant, requirements and supervisor. With respect to the control ow, we consider event-based models as well as state-based ones. We study the process theory TCP as a convenient modeling formalism that includes parallelism, iteration, communication features and non-determinism. Via structural operational semantics, we relate the terms in TCP to labeled transition systems. We consider the partial bisimulation preorder to express controllability that is better suited to handle non-determinism, compared to bisimulation-based models. It is shown how precongruence of partial bisimulation can be derived from the format of the deduction rules. The theory of TCP is studied under nite axiomatization for which soundness and ground-completeness (modulo iteration) is proved with respect to partial bisimulation. Language-based controllability, as the neccesary condition for event-based supervisory control is expressed in terms of partial bisimulation and we discuss several drawbacks of the strict event-based approach. Statebased control is considered under partial bisimulation as a dependable solution to address non-determinism. An appropriate renaming operator is introduced to address an issue in parallel communication. A case for automated guided vehicles (AGV) is modeled using the theory TCP. The latter theory is henceforth extended to include state-based valuations for which partial bisimulation and an axiomatization are dened. We consider an extended case on industrial printers to show the modeling abilities of this extended theory. In our concluding remarks, we sketch a future research path in terms of a new formal language for concurrent control modeling
Reconciling real and stochastic time: The need for probabilistic refinement
We conservatively extend anACP-style discrete-time process theorywith discrete stochastic delays. The semantics of the timed delays relies on time additivity and time determinism, which are properties that enable us to merge subsequent timed delays and to impose their synchronous expiration. Stochastic delays, however, interact with respect to a so-called race condition that determines the set of delays that expire first, which is guided by an (implicit) probabilistic choice. The race condition precludes the property of time additivity as the merger of stochastic delays alters this probabilistic behavior. To this end, we resolve the race condition using conditionally- distributed unit delays. We give a sound and ground-complete axiomatization of the process theory comprising the standard set of ACP-style operators. In this generalized setting, the alternative composition is no longer associative, so we have to resort to special normal forms that explicitly resolve the underlying race condition. Our treatment succeeds in the initial challenge to conservatively extend standard time with stochastic time. However, the 'dissection' of the stochastic delays to conditionally-distributed unit delays comes at a price, as we can no longer relate the resolved race condition to the original stochastic delays. We seek a solution in the field of probabilistic refinements that enable the interchange of probabilistic and non deterministic choices.Fil: Markovski, J.. Technische Universiteit Eindhoven; Países BajosFil: D'argenio, Pedro Ruben. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Baeten, J. C. M.. Technische Universiteit Eindhoven; Países Bajos. Centrum Wiskunde & Informatica; Países BajosFil: De Vink, E. P.. Technische Universiteit Eindhoven; Países Bajos. Centrum Wiskunde & Informatica; Países Bajo
Public Key Block Cipher Based on Multivariate Quadratic Quasigroups
We have designed a new class of public
key algorithms based on quasigroup string transformations using a
specific class of quasigroups called \emph{multivariate quadratic
quasigroups (MQQ)}. Our public key algorithm is a bijective mapping,
it does not perform message expansions and can be used both for
encryption and signatures. The public key consist of quadratic
polynomials with variables where . A
particular characteristic of our public key algorithm is that it is
very fast and highly parallelizable. More concretely, it has the
speed of a typical modern symmetric block cipher -- the reason for
the phrase \emph{ A Public Key Block Cipher } in the title of this
paper. Namely the reference C code for the 160--bit variant of the
algorithm performs decryption in less than 11,000 cycles (on Intel
Core 2 Duo -- using only one processor core), and around 6,000
cycles using two CPU cores and OpenMP 2.0 library. However,
implemented in Xilinx Virtex-5 FPGA that is running on 249.4 MHz it
achieves decryption throughput of 399 Mbps, and implemented on four
Xilinx Virtex-5 chips that are running on 276.7 MHz it achieves
encryption throughput of 44.27 Gbps. Compared to fastest RSA
implementations on similar FPGA platforms, MQQ algorithm is more
than 10,000 times faster
Location prediction based on a sector snapshot for location-based services
In location-based services (LBSs), the service is provided based on the users' locations through location determination and mobility realization. Most of the current location prediction research is focused on generalized location models, where the geographic extent is divided into regular-shaped cells. These models are not suitable for certain LBSs where the objectives are to compute and present on-road services. Such techniques are the new Markov-based mobility prediction (NMMP) and prediction location model (PLM) that deal with inner cell structure and different levels of prediction, respectively. The NMMP and PLM techniques suffer from complex computation, accuracy rate regression, and insufficient accuracy. In this paper, a novel cell splitting algorithm is proposed. Also, a new prediction technique is introduced. The cell splitting is universal so it can be applied to all types of cells. Meanwhile, this algorithm is implemented to the Micro cell in parallel with the new prediction technique. The prediction technique, compared with two classic prediction techniques and the experimental results, show the effectiveness and robustness of the new splitting algorithm and prediction technique
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