| 1. |
- Khamespanah, Ehsan, et al.
(författare)
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State Distribution Policy for Distributed Model Checking of Actor Models
- 2015
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Ingår i: Electronic Communications of the EASST. - Berlin : Universitätsverlag der TU Berlin. - 1863-2122. ; 72, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Model checking temporal properties is often reduced to finding accepting cycles in Büchi automata. A key ingredient for an effective distributed model checking technique is a distribution policy that does not split the potential accepting cycles of the corresponding automaton among several nodes. In this paper, we introduce a distribution policy to reduce the number of split cycles. This policy is based on the call dependency graph, obtained from the message passing skeleton of the model. We prove theoretical results about the correspondence between the cycles of call dependency graph and the cycles of the concrete state space and provide empirical data obtained from applying our distribution policy in state space generation and reachability analysis. We take Rebeca, an imperative interpretation of actors, as our modeling language and implement the introduced policy in its distributed state space generator. Our technique can be applied to other message-driven actor-based models where concurrent objects or services are units of concurrency.
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| 2. |
- Jaghoori, Mohammad Mahdi, et al.
(författare)
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Symmetry and partial order reduction techniques in model checking Rebeca
- 2010
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Ingår i: Acta Informatica. - New York : Springer. - 0001-5903 .- 1432-0525. ; 47:1, s. 33-66
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Tidskriftsartikel (refereegranskat)abstract
- Rebeca is an actor-based language with formal semantics which is suitable for modeling concurrent and distributed systems and protocols. Due to its object model, partial order and symmetry detection and reduction techniques can be efficiently applied to dynamic Rebecamodels. We present two approaches for detecting symmetry in Rebeca models: One that detects symmetry in the topology of inter-connections among objects and another one which exploits specific data structures to reflect internal symmetry in the internal structure of an object. The former approach is novel in that it does not require any input from the modeler and can deal with the dynamic changes of topology. This approach is potentially applicable to a wide range of modeling languages for distributed and reactive systems. We have also developed a model checking tool that implements all of the above-mentioned techniques. The evaluation results show significant improvements in model size and model-checkingtime.
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| 3. |
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| 4. |
- Khakpour, Narges, et al.
(författare)
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Formal modeling of evolving self-adaptive systems
- 2012
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Ingår i: Science of Computer Programming. - Amsterdam : Elsevier. - 0167-6423 .- 1872-7964. ; 78:1, s. 3-26
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a formal model, named PobSAM (Policy-based Self-Adaptive Model), for developing and modeling self-adaptive evolving systems. In this model, policies are used as a mechanism to direct and adapt the behavior of self-adaptive systems. A PobSAM model is a collection of autonomous managers and managed actors. The managed actors are dedicated to the functional behavior while the autonomous managers govern the behavior of managed actors by enforcing suitable policies. A manager has a set of configurations including two types of policies: governing policies and adaptation policies. To adapt the system behavior in response to the changes, the managers switch among different configurations. We employ the combination of an algebraic formalism and an actor-based model to specify this model formally. Managed actors are expressed by an actor model. Managers are modeled as meta-actors whose configurations are described using a multi-sorted algebra called CA. We provide an operational semantics for PobSAM using labeled transition systems. Furthermore, we provide behavioral equivalence of different sorts of CA in terms of splitting bisimulation and prioritized splitting bisimulation. Equivalent managers send the same set of messages to the actors. Using our behavioral equivalence theory, we can prove that the overall behavior of the system is preserved by substituting a manager by an equivalent one.
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| 5. |
- Hojjat, Hossein, et al.
(författare)
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A framework for performance evaluation and functional verification in stochastic process algebras
- 2008
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Ingår i: SAC '08. - New York : Association for Computing Machinery (ACM). - 9781595937537 ; , s. 339-346
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Konferensbidrag (refereegranskat)abstract
- Despite its relatively short history, a wealth of formalisms exist for algebraic specification of stochastic systems. The goal of this paper is to give such formalisms a unifying framework for performance evaluation and functional verification. To this end, we propose an approach enabling a provably sound transformation from some existing stochastic process algebras, e.g., PEPA and MTIPP, to a generic form in the mCRL2 language. This way, we resolve the semantic differences among different stochastic process algebras themselves, on one hand, and between stochastic process algebras and classic ones, such as mCRL2, on the other hand. From the generic form, one can generate a state space and perform various functional and performance-related analyses, as we illustrate in this paper.
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| 6. |
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| 7. |
- Hojjat, Hossein, et al.
(författare)
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Formal analysis of systemc designs in process algebra
- 2011
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Ingår i: Fundamenta Informaticae. - Amsterdam : IOS Press. - 0169-2968 .- 1875-8681. ; 107, s. 19-42
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Tidskriftsartikel (refereegranskat)abstract
- SystemC is an IEEE standard system-level language used in hardware/software co-design and has been widely adopted in the industry. This paper describes a formal approach to verifying SystemC designs by providing a mapping to the process algebra mCRL2. Our mapping formalizes both the simulation semantics as well as exhaustive state-space exploration of SystemC designs. By exploiting the existing reduction techniques of mCRL2 and also its model-checking tools, we efficiently locate the race conditions in a system and resolve them. A tool is implemented to automatically perform the proposed mapping. This mapping and the implemented tool enabled us to exploit process-algebraic verification techniques to analyze a number of case-studies, including the formal analysis of a single-cycle and a pipelined MIPS processor specified in SystemC.
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| 8. |
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| 9. |
- Marksteiner, Stefan
(författare)
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Model-Driven Security Test Case Generation Using Threat Modeling and Automata Learning
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Automotive systems are not only becoming more open through developments like advanced driving assistance functions, autonomous driving, vehicle-to-everything communication and software-defined vehicle functionality, but also more complex. At the same time, technology from standard IT systems become frequently adopted in this setting. These developments have two negative effects on correctness and security: the rising complexity adds potential flaws and vulnerabilities while the increased openness expands attack surfaces and entry points for adversaries. To provide more secure systems, the amount of verifying system security through testing has to be significantly increased, which is also a requirement by international regulation and standards. Due to long supply chains and non-disclosure policies, verification methods often have to operate in a black box setting. This thesis strives therefore towards finding more efficient methods of automating test case generation in both white and black box scenarios. The focus lies on communication protocols used in vehicular systems. The main approaches used are model-based methods. We provide a practical method to automatically obtain behavioral models in the form of state machines of communication protocol implementations in real-world settings using automata learning. We also provide a means to automatically check these implementation models for their compliance with a specification (e.g., from a standard). We furthermore present a technique to automatically derive test-cases to point out found deviations on the actual system.We also present a method to create abstract cybersecurity test case specifications from semi-formal threat models using attack trees.
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