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  • 1. Aarts, Fides
    et al.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Uijen, Johan
    Vaandrager, Frits
    Generating models of infinite-state communication protocols using regular inference with abstraction2015In: Formal methods in system design, ISSN 0925-9856, E-ISSN 1572-8102, Vol. 46, no 1, p. 1-41Article in journal (Refereed)
    Abstract [en]

    In order to facilitate model-based verification and validation, effort is underway to develop techniques for generating models of communication system components from observations of their external behavior. Most previous such work has employed regular inference techniques which generate modest-size finite-state models. They typically suppress parameters of messages, although these have a significant impact on control flow in many communication protocols. We present a framework, which adapts regular inference to include data parameters in messages and states for generating components with large or infinite message alphabets. A main idea is to adapt the framework of predicate abstraction, successfully used in formal verification. Since we are in a black-box setting, the abstraction must be supplied externally, using information about how the component manages data parameters. We have implemented our techniques by connecting the LearnLib tool for regular inference with an implementation of session initiation protocol (SIP) in ns-2 and an implementation of transmission control protocol (TCP) in Windows 8, and generated models of SIP and TCP components.

  • 2.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Cyriac, Aiswarya
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Chennai Math Inst, Madras, Tamil Nadu, India..
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Data Communicating Processes with Unreliable Channels2016In: Proceedings Of The 31St Annual ACM-IEEE Symposium On Logic In Computer Science (LICS 2016), 2016, p. 166-175Conference paper (Refereed)
    Abstract [en]

    We extend the classical model of lossy channel systems by considering systems that operate on a finite set of variables ranging over an infinite data domain. Furthermore, each message inside a channel is equipped with a data item representing its value. Although we restrict the model by allowing the variables to be only tested for (dis-)equality, we show that the state reachability problem is undecidable. In light of this negative result, we consider bounded-phase reachability, where the processes are restricted to performing either send or receive operations during each phase. We show decidability of state reachability in this case by computing a symbolic encoding of the set of system configurations that are reachable from a given configuration.

  • 3.
    Abdulla, Parosh A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Univ Genoa, DIBRIS, Genoa, Italy..
    Parameterized verification2016In: International Journal on Software Tools for Technology Transfer (STTT), ISSN 1433-2779, E-ISSN 1433-2787, Vol. 18, no 5, p. 469-473Article in journal (Other academic)
    Abstract [en]

    The goal of parameterized verification is to prove the correctness of a system specification regardless of the number of its components. The problem is of interest in several different areas: verification of hardware design, multithreaded programs, distributed systems, and communication protocols. The problem is undecidable in general. Solutions for restricted classes of systems and properties have been studied in areas like theorem proving, model checking, automata and logic, process algebra, and constraint solving. In this introduction to the special issue, dedicated to a selection of works from the Parameterized Verification workshop PV '14 and PV '15, we survey some of the works developed in this research area.

  • 4.
    Abdulla, Parosh A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Univ Genoa, Genoa, Italy..
    Montali, Marco
    Free Univ Bolzano, Bolzano, Italy..
    Well Structured Transition Systems with History2015In: Electronic Proceedings in Theoretical Computer Science, ISSN 2075-2180, E-ISSN 2075-2180, no 193, p. 115-128Article in journal (Refereed)
    Abstract [en]

    We propose a formal model of concurrent systems in which the history of a computation is explicitly represented as a collection of events that provide a view of a sequence of configurations. In our model events generated by transitions become part of the system configurations leading to operational semantics with historical data. This model allows us to formalize what is usually done in symbolic verification algorithms. Indeed, search algorithms often use meta-information, e.g., names of fired transitions, selected processes, etc., to reconstruct (error) traces from symbolic state exploration. The other interesting point of the proposed model is related to a possible new application of the theory of well-structured transition systems (wsts). In our setting wsts theory can be applied to formally extend the class of properties that can be verified using coverability to take into consideration (ordered and unordered) historical data. This can be done by using different types of representation of collections of events and by combining them with wsts by using closure properties of well-quasi orderings.

  • 5.
    Abdulla, Parosh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Aronis, Stavros
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Comparing source sets and persistent sets for partial order reduction2017In: Models, Algorithms, Logics and Tools: Essays dedicated to Kim Guldstrand Larsen on the occasion of his 60th birthday, Springer, 2017, p. 516-536Chapter in book (Other academic)
  • 6.
    Abdulla, Parosh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Aronis, Stavros
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Source Sets: A Foundation for Optimal Dynamic Partial Order Reduction2017In: Journal of the ACM, ISSN 0004-5411, E-ISSN 1557-735X, Vol. 64, no 4, article id 25Article in journal (Refereed)
    Abstract [en]

    Stateless model checking is a powerful method for program verification that, however, suffers from an exponential growth in the number of explored executions. A successful technique for reducing this number, while still maintaining complete coverage, is Dynamic Partial Order Reduction (DPOR), an algorithm originally introduced by Flanagan and Godefroid in 2005 and since then not only used as a point of reference but also extended by various researchers. In this article, we present a new DPOR algorithm, which is the first to be provably optimal in that it always explores the minimal number of executions. It is based on a novel class of sets, called source sets, that replace the role of persistent sets in previous algorithms. We begin by showing how to modify the original DPOR algorithm to work with source sets, resulting in an efficient and simple-to-implement algorithm, called source-DPOR. Subsequently, we enhance this algorithm with a novel mechanism, called wakeup trees, that allows the resulting algorithm, called optimal-DPOR, to achieve optimality. Both algorithms are then extended to computational models where processes may disable each other, for example, via locks. Finally, we discuss tradeoffs of the source-and optimal-DPOR algorithm and present programs that illustrate significant time and space performance differences between them. We have implemented both algorithms in a publicly available stateless model checking tool for Erlang programs, while the source-DPOR algorithm is at the core of a publicly available stateless model checking tool for C/pthread programs running on machines with relaxed memory models. Experiments show that source sets significantly increase the performance of stateless model checking compared to using the original DPOR algorithm and that wakeup trees incur only a small overhead in both time and space in practice.

  • 7.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Aronis, Stavros
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Leonardsson, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Stateless model checking for TSO and PSO2015In: Tools and Algorithms for the Construction and Analysis of Systems: TACAS 2015, Springer Berlin/Heidelberg, 2015, p. 353-367Conference paper (Refereed)
  • 8.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Aronis, Stavros
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Leonardsson, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Stateless model checking for TSO and PSO2017In: Acta Informatica, ISSN 0001-5903, E-ISSN 1432-0525, Vol. 54, no 8, p. 789-818Article in journal (Refereed)
  • 9.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    Ngo, Tuan Phong
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A load-buffer semantics for total store ordering2018In: Logical Methods in Computer Science, ISSN 1860-5974, E-ISSN 1860-5974, Vol. 14, no 1, article id 9Article in journal (Refereed)
  • 10.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    Ngo, Tuan Phong
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Context-bounded analysis for POWER2017In: Tools and Algorithms for the Construction and Analysis of Systems: Part II, Springer, 2017, p. 56-74Conference paper (Refereed)
  • 11.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    Ngo, Tuan Phong
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    The benefits of duality in verifying concurrent programs under TSO2016In: 27th International Conference on Concurrency Theory: CONCUR 2016, Dagstuhl, Germany: Leibniz-Zentrum für Informatik , 2016, p. 5:1-15Conference paper (Refereed)
  • 12.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bui, Phi Diep
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Counter-Example Guided Program Verification2016In: FM 2016: Formal Methods, Springer, 2016, p. 25-42Conference paper (Refereed)
  • 13.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Cederberg, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Modi, Subham
    Rezine, Othmane
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Saini, Gaurav
    MPass: An efficient tool for the analysis of message-passing programs2015In: Formal Aspects of Component Software, Springer, 2015, p. 198-206Conference paper (Refereed)
  • 14.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Chen, Yu-Fang
    Bui, Phi Diep
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Holık, Lukas
    Rezine, Ahmed
    Rümmer, Philipp
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Flatten and Conquer: A Framework for Efficient Analysis of String Constraints2017In: SIGPLAN notices, ISSN 0362-1340, E-ISSN 1558-1160, Vol. 52, no 6, p. 602-617Article in journal (Refereed)
    Abstract [en]

    We describe a uniform and efficient framework for checking the satisfiability of a large class of string constraints. The framework is based on the observation that both satisfiability and unsatisfiability of common constraints can be demonstrated through witnesses with simple patterns. These patterns are captured using flat automata each of which consists of a sequence of simple loops. We build a Counter-Example Guided Abstraction Refinement (CEGAR) framework which contains both an under-and an over-approximation module. The flow of information between the modules allows to increase the precision in an automatic manner. We have implemented the framework as a tool and performed extensive experimentation that demonstrates both the generality and efficiency of our method.

  • 15.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Chen, Yu-Fang
    Holík, Lukás
    Rezine, Ahmed
    Rümmer, Philipp
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Stenman, Jari
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Norn: An SMT solver for string constraints2015In: Computer Aided Verification: Part I, Springer, 2015, p. 462-469Conference paper (Refereed)
    Abstract [en]

    We present version 1.0 of the Norn SMT solver for string constraints. Norn is a solver for an expressive constraint language, including word equations, length constraints, and regular membership queries. As a feature distinguishing Norn from other SMT solvers, Norn is a decision procedure under the assumption of a set of acyclicity conditions on word equations, without any restrictions on the use of regular membership.

  • 16.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Ganjei, Zeinab
    Rezine, Ahmed
    Zhu, Yunyun
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Verification of Cache Coherence Protocols wrt. Trace Filters2015In: Proc. 15th Conference on Formal Methods in Computer-Aided Design, Piscataway, NJ: IEEE , 2015, p. 9-16Conference paper (Refereed)
  • 17.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Leonardsson, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Stateless model checking for POWER2016In: Computer Aided Verification: Part II, Springer, 2016, p. 134-156Conference paper (Refereed)
    Abstract [en]

    We present the first framework for efficient application of stateless model checking (SMC) to programs running under the relaxed memory model of POWER. The framework combines several contributions. The first contribution is that we develop a scheme for systematically deriving operational execution models from existing axiomatic ones. The scheme is such that the derived execution models are well suited for efficient SMC. We apply our scheme to the axiomatic model of POWER from [8]. Our main contribution is a technique for efficient SMC, called Relaxed Stateless Model Checking (RSMC), which systematically explores the possible inequivalent executions of a program. RSMC is suitable for execution models obtained using our scheme. We prove that RSMC is sound and optimal for the POWER memory model, in the sense that each complete program behavior is explored exactly once. We show the feasibility of our technique by providing an implementation for programs written in C/pthreads.

  • 18.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Kara, Ahmet
    Rezine, Othmane
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Verification of buffered dynamic register automata2015In: Networked Systems: NETYS 2015, Springer, 2015, p. 15-31Conference paper (Refereed)
  • 19.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Kaxiras, Stefanos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Leonardsson, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Ros, Alberto
    Zhu, Yunyun
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Fencing programs with self-invalidation and self-downgrade2016In: Formal Techniques for Distributed Objects, Components, and Systems, Springer, 2016, p. 19-35Conference paper (Refereed)
  • 20.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Kaxiras, Stefanos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Leonardsson, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Ros, Alberto
    Zhu, Yunyun
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Mending fences with self-invalidation and self-downgrade2018In: Logical Methods in Computer Science, ISSN 1860-5974, E-ISSN 1860-5974, Vol. 14, no 1, article id 6Article in journal (Refereed)
  • 21.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Lång, Magnus
    Ngo, Tuan Phong
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Precise and sound automatic fence insertion procedure under PSO2015In: Networked Systems: NETYS 2015, Springer, 2015, p. 32-47Conference paper (Refereed)
  • 22.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Meyer, Roland
    Salehi, Mehdi Seyed
    What's decidable about availability languages?2015In: Proc. 35th IARCS Conference on Foundation of Software Technology and Theoretical Computer Science, Dagstuhl, Germany: Leibniz-Zentrum für Informatik , 2015, p. 192-205Conference paper (Refereed)
  • 23.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Ngo, Tuan-Phong
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    The Best of Both Worlds: Trading efficiency and optimality in fence insertion for TSO2015In: Programming Languages and Systems: ESOP 2015, Springer Berlin/Heidelberg, 2015, p. 308-332Conference paper (Refereed)
    Abstract [en]

    We present a method for automatic fence insertion in concurrent programs running under weak memory models that provides the best known trade-off between efficiency and optimality. On the one hand, the method can efficiently handle complex aspects of program behaviors such as unbounded buffers and large numbers of processes. On the other hand, it is able to find small sets of fences needed for ensuring correctness of the program. To this end, we propose a novel notion of correctness, called persistence, that compares the behavior of the program under the weak memory semantics with that under the classical interleaving (SC) semantics. We instantiate our framework for the Total Store Ordering (TSO) memory model, and give an algorithm that reduces the fence insertion problem under TSO to the reachability problem for programs running under SC. Furthermore, we provide an abstraction scheme that substantially increases scalability to large numbers of processes. Based on our method, we have implemented a tool and run it successfully on a wide range benchmarks.

  • 24.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Univ Genoa, I-16126 Genoa, Italy..
    Rezine, Othmane
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Uppsala Univ, Uppsala, Sweden..
    Sangnier, Arnaud
    Univ Paris Diderot, CNRS, LIAFA, Paris, France..
    Traverso, Riccardo
    FBK, Trento, Italy..
    Parameterized verification of time-sensitive models of ad hoc network protocols2016In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 612, p. 1-22Article in journal (Refereed)
    Abstract [en]

    We study decidability and undecidability results for parameterized verification of a formal model of timed Ad Hoc network protocols. The communication topology is defined by an undirected graph and the behaviour of each node is defined by a timed automaton communicating with its neighbours via broadcast messages. We consider parameterized verification problems formulated in terms of reachability. In particular we are interested in searching for an initial configuration from which an individual node can reach an error state. We study the problem for dense and discrete time and compare the results with those obtained for (fully connected) networks of timed automata.

  • 25.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Haziza, Frédéric
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Holík, Lukás
    Brno Univ Technol, Brno, Czech Republic.
    Parameterized verification through view abstraction2016In: International Journal on Software Tools for Technology Transfer (STTT), ISSN 1433-2779, E-ISSN 1433-2787, Vol. 18, no 5, p. 495-516Article in journal (Refereed)
    Abstract [en]

    We present a simple and efficient framework for automatic verification of systems with a parametric number of communicating processes. The processes may be organized in various topologies such as words, multisets, rings, or trees. Our method needs to inspect only a small number of processes in order to show correctness of the whole system. It relies on an abstraction function that views the system from the perspective of a fixed number of processes. The abstraction is used during the verification procedure in order to dynamically detect cut-off points beyond which the search of the state space need not continue. We show that the method is complete for a large class of well quasi-ordered systems including Petri nets. Our experimentation on a variety of benchmarks demonstrate that the method is highly efficient and that it works well even for classes of systems with undecidable verification problems. In particular, the method handles the fine-grained and full version of Szymanski's mutual exclusion protocol, whose correctness, to the best of our knowledge, has not been proven automatically by any other existing methods.

  • 26.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Holík, Lukás
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Lengál, Ondrej
    Trinh, Cong Quy
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Vojnar, Tomás
    Verification of heap manipulating programs with ordered data by extended forest automata2016In: Acta Informatica, ISSN 0001-5903, E-ISSN 1432-0525, Vol. 53, no 4, p. 357-385Article in journal (Refereed)
    Abstract [en]

    We present a general framework for verifying programs with complex dynamic linked data structures whose correctness depends on ordering relations between stored data values. The underlying formalism of our framework is that of forest automata (FA), which has previously been developed for verification of heap-manipulating programs. We extend FA with constraints between data elements associated with nodes of the heaps represented by FA, and we present extended versions of all operations needed for using the extended FA in a fully-automated verification approach, based on abstract interpretation. We have implemented our approach as an extension of the Forester tool and successfully applied it to a number of programs dealing with data structures such as various forms of singly- and doubly-linked lists, binary search trees, as well as skip lists.

  • 27.
    Abdulla, Parosh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Ciobanu, Radu
    Univ Edinburgh, Edinburgh, Midlothian, Scotland..
    Mayr, Richard
    Univ Edinburgh, Edinburgh, Midlothian, Scotland..
    Sangnier, Arnaud
    Univ Paris Diderot, CNRS, LIAFA, Sorbonne Paris Cite, Paris, France..
    Sproston, Jeremy
    Univ Turin, Turin, Italy..
    Qualitative Analysis of VASS-Induced MDPs2016In: Foundations Of Software Science And Computation Structures (FOSSACS 2016) / [ed] Jacobs, B Loding, C, 2016, p. 319-334Conference paper (Refereed)
    Abstract [en]

    We consider infinite-state Markov decision processes (MDPs) that are induced by extensions of vector addition systems with states (VASS). Verification conditions for these MDPs are described by reachability and Buchi objectives w.r.t. given sets of control-states. We study the decidability of some qualitative versions of these objectives, i.e., the decidability of whether such objectives can be achieved surely, almostsurely, or limit-surely. While most such problems are undecidable in general, some are decidable for large subclasses in which either only the controller or only the random environment can change the counter values (while the other side can only change control-states).

  • 28.
    Abdulla, Parosh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Haziza, Frédéric
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Holík, Lukás
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Brno Univ Technol, Brno, Czech Republic..
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rezine, Ahmed
    Linköping Univ, Linköping, Sweden..
    An integrated specification and verification technique for highly concurrent data structures for highly concurrent data structures2017In: International Journal on Software Tools for Technology Transfer (STTT), ISSN 1433-2779, E-ISSN 1433-2787, Vol. 19, no 5, p. 549-563Article in journal (Refereed)
    Abstract [en]

    We present a technique for automatically verifying safety properties of concurrent programs, in particular programs that rely on subtle dependencies of local states of different threads, such as lock-free implementations of stacks and queues in an environment without garbage collection. Our technique addresses the joint challenges of infinite-state specifications, an unbounded number of threads, and an unbounded heap managed by explicit memory allocation. Our technique builds on the automata-theoretic approach to model checking, in which a specification is given by an automaton that observes the execution of a program and accepts executions that violate the intended specification. We extend this approach by allowing specifications to be given by a class of infinite-state automata. We show how such automata can be used to specify queues, stacks, and other data structures, by extending a data-independence argument. For verification, we develop a shape analysis, which tracks correlations between pairs of threads, and a novel abstraction to make the analysis practical. We have implemented our method and used it to verify programs, some of which have not been verified by any other automatic method before.

  • 29.
    Abdulla, Parosh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Jonsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Trinh, Cong Quy
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Automated Verification of Linearization Policies2016In: Automated Verification of Linearization Policies: 23rd International Symposium, SAS 2016, Edinburgh, UK, September 8-10, 2016, Proceedings, 2016Conference paper (Other academic)
    Abstract [en]

    We present a novel framework for automated verification of linearizability for concurrent data structures that implement sets, stacks, and queues. The framework requires the user to provide a linearization policy, which describes how linearization point placement in different concurrent threads affect each other; such linearization policies are often provided informally together with descriptions of new algorithms. We present a specification formalism for linearization policies which allows the user to specify, in a simple and concise manner, complex patterns including non-fixed linearization points. To automate verification, we extend thread-modular reasoning to bound the number of considered threads, and use a novel symbolic representation for unbounded heap structures that store data from an unbounded domain. We have implemented our framework in a tool and successfully used it to prove linearizability for a wide range of algorithms, including all implementations of concurrent sets, stacks, and queues based on singly-linked lists that are known to us from the literature.

  • 30.
    Abdullah, Jakaria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Mohaqeqi, Morteza
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Yi, Wang
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Synthesis of Ada code from graph-based task models2017In: Proc. 32nd ACM Symposium on Applied Computing, New York: ACM Press, 2017, p. 1467-1472Conference paper (Refereed)
  • 31.
    Abdullah, Syed Md Jakaria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Lampka, Kai
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Yi, Wang
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Improving performance by monitoring while maintaining worst-case guarantees2016In: Proc. 19th Conference on Design, Automation and Test in Europe, Piscataway, NJ: IEEE, 2016, p. 257-260Conference paper (Refereed)
  • 32. Ahlgren, Bengt
    et al.
    Hidell, Markus
    Ngai, Edith C.-H.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Internet of Things for smart cities: Interoperability and open data2016In: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 20, no 6, p. 52-56Article in journal (Refereed)
  • 33.
    Alipour, Mehdi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Carlson, Trevor E.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Kaxiras, Stefanos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A Taxonomy of Out-of-Order Instruction Commit2017In: 2017 Ieee International Symposium On Performance Analysis Of Systems And Software (Ispass), Los Alamitos: IEEE Computer Society, 2017, p. 135-136Conference paper (Refereed)
    Abstract [en]

    While in-order instruction commit has its advantages, such as providing precise interrupts and avoiding complications with the memory consistency model, it requires the core to hold on to resources (reorder buffer entries, load/store queue entries, registers) until they are released in program order. In contrast, out-of-order commit releases resources much earlier, yielding improved performance without the need for additional hardware resources. In this paper, we revisit out-of-order commit from a different perspective, not by proposing another hardware technique, but by introducing a taxonomy and evaluating three different micro-architectures that have this technique enabled. We show how smaller processors can benefit from simple out-oforder commit strategies, but that larger, aggressive cores require more aggressive strategies to improve performance.

  • 34.
    Amanda, Nordhamn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Design and implementation of a demonstrator for a Bluetooth Low Energy based fleet service system for hand-held gardening and forestry products2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today, large companies specialized in forestry or park maintenance may own very large machine fleets consisting of hundreds of trimmers, chainsaws and brush cutters. Husqvarna Group, whose core business lies within high-end forestry and gardening products, has noticed that such companies tend to buy cheaper, low quality forestry and gardening products. The reason is thought to be that the companies lack a proper overview of the service status and utilization levels of their machines, leading to insufficient service, causing machines to break prematurely and making it hard to motivate investments in more expensive products. Hence, the companies usually adopt a consumerist approach, and buy cheaper products that are thrown away upon breaking.

    To make their products more attractive to machine park owners, Husqvarna want to explore the area of Internet of Things and equip their machines with sensing and communication capabilities. Collected data could be used to provide an overview of machine usage and service requirements to the machine parks owners, and could make it easier for machine park owners to dimension their machine fleet. In addition to this, a machine monitoring system where specific operator behavior can be tracked could enable identification of operators who consistently mistreat their machines by, for example, running the machine engine at non-optimal rotation speeds.

    In this master's thesis, a demonstrator of the working principle of a Bluetooth Low Energy based Fleet Service System is designed and implemented, complete with an evaluation of if received signal strength indicator (RSSI) is a good enough distance estimator to determine which operator operates a certain machine. 

    Experiments carried out indicate that while RSSI is not a good estimator of distance, it could be used to determine the operator in closest proximity given that operators are not allowed to work closer than within a 10 m radius of each other.

  • 35.
    Ashcroft, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Fisher, Ali
    Univ Vienna, VORTEX, Vienna, Austria.
    Kaati, Lisa
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Omer, Enghin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Prucha, Nico
    Kings Coll London, ICSR, London, England.
    Detecting jihadist messages on twitter2015In: Proc. 5th European Intelligence and Security Informatics Conference, IEEE Computer Society, 2015, p. 161-164Conference paper (Refereed)
    Abstract [en]

    Jihadist groups such as ISIS are spreading online propaganda using various forms of social media such as Twitter and YouTube. One of the most common approaches to stop these groups is to suspend accounts that spread propaganda when they are discovered. This approach requires that human analysts manually read and analyze an enormous amount of information on social media. In this work we make a first attempt to automatically detect messages released by jihadist groups on Twitter. We use a machine learning approach that classifies a tweet as containing material that is supporting jihadists groups or not. Even tough our results are preliminary and more tests needs to be carried out we believe that results indicate that an automated approach to aid analysts in their work with detecting radical content on social media is a promising way forward. It should be noted that an automatic approach to detect radical content should only be used as a support tool for human analysts in their work.

  • 36.
    Ashcroft, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Johansson, Fredrik
    Swedish Def Res Agcy FOI, Stockholm, Sweden..
    Kaati, Lisa
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Swedish Def Res Agcy FOI, Stockholm, Sweden..
    Shrestha, Amendra
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Multi-domain alias matching using machine learning2016In: Proc. 3rd European Network Intelligence Conference, IEEE, 2016, p. 77-84Conference paper (Refereed)
    Abstract [en]

    We describe a methodology for linking aliases belonging to the same individual based on a user's writing style (stylometric features extracted from the user generated content) and her time patterns (time-based features extracted from the publishing times of the user generated content). While most previous research on social media identity linkage relies on matching usernames, our methodology can also be used for users who actively try to choose dissimilar usernames when creating their aliases. In our experiments on a discussion forum dataset and a Twitter dataset, we evaluate the performance of three different classifiers. We use the best classifier (AdaBoost) to evaluate how well it works on different datasets using different features. Experiments show that combining stylometric and time based features yield good results on our synthetic datasets and a small-scale evaluation on real-world blog data confirm these results, yielding a precision over 95%. The use of emotion-related and Twitter-related features yield no significant impact on the results.

  • 37.
    Ashcroft, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Kaati, Lisa
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. FOI, Stockholm, Sweden.
    Meyer, Maxime
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A step towards detecting online grooming: Identifying adults pretending to be children2015In: Proc. 5th European Intelligence and Security Informatics Conference, IEEE Computer Society, 2015, p. 98-104Conference paper (Refereed)
    Abstract [en]

    Online grooming is a major problem in todays society where more and more time is spent online. To become friends and establish a relationship with their young victims in online communities, groomers often pretend to be children. In this paper we describe an approach that can be used to detect if an adult is pretending to be a child in a chat room conversation. The approach involves a two step process wherein authors are first classified as being children or adults, and then each child is being examined and false children distinguished from genuine children. Our results show that even if it is hard to separate ordinary adults from children in chat logs it is possible to distinguish real children from adults pretending to be children with a high accuracy. In this paper we will discuss the accuracy of the methods proposed, as well as the features that were important in their success. We believe that this work is an important step towards automated analysis of chat room conversation to detect and possible attempts of grooming. Our approach where we use text analysis to distinguish adults who are pretending to be children from actual children could be used to inform children about the true age of the person that they are communicating. This would be a step towards making the Internet more secure for young children and eliminate grooming.

  • 38.
    Ashcroft, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Kaati, Lisa
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Meyer, Maxime
    Are You Really a Child?: A Machine Learning Approach To Protect Children from Online Grooming2015In: Proc. National Symposium on Technology and Methodology for Security and Crisis Management: TAMSEC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    Online grooming and sexual abuse of children is a major threat towards the security of todays society where more and more time is spent online. To become friends and establish a relationship with their young victims in online communities, groomers often pretend to be children. In this work we describe an approach that can be used to detect if an adult is pretending to be a child in a chat room conversation. Our results show that even if it is hard to separate ordinary adults from children in chat logs it is possible to distinguish real children from adults pretending to be children with a high accuracy.

  • 39.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bollig, Benedikt
    CNRS, LSV, Paris, France.;ENS Paris Saclay, Paris, France.
    Habermehl, Peter
    CNRS, IRIF, Paris, France.;Univ Paris Diderot, Paris, France..
    Emptiness of Ordered Multi-Pushdown Automata is 2ETIME-Complete2017In: International Journal of Foundations of Computer Science, ISSN 0129-0541, Vol. 28, no 8, p. 945-975Article in journal (Refereed)
    Abstract [en]

    We consider ordered multi-pushdown automata, a multi-stack extension of pushdown automata that comes with a constraint on stack operations: a pop can only be performed on the first non-empty stack (which implies that we assume a linear ordering on the collection of stacks). We show that the emptiness problem for multi-pushdown automata is 2ETIME-complete. Containment in 2ETIME is shown by translating an automaton into a grammar for which we can check if the generated language is empty. The lower bound is established by simulating the behavior of an alternating Turing machine working in exponential space. We also compare ordered multi-pushdown automata with the model of bounded-phase (visibly) multi-stack pushdown automata, which do not impose an ordering on stacks, but restrict the number of alternations of pop operations on different stacks.

  • 40.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    LIAFA, CNRS and University of Paris Diderot.
    Kumar, K. Narayan
    Chennai Mathematical Institute, Chennai, India.
    Saivasan, Prakash
    TU Braunschweig, Germany.
    Parity Games on Bounded Phase Multi-pushdown Systems2017In: Networked Systems: 5th International Conference, NETYS 2017, Marrakech, Morocco, May 17-19, 2017, Proceedings / [ed] Amr El Abbadi and Benoit Garbinato, Cham, 2017, Vol. 10299, p. 272-287Conference paper (Refereed)
    Abstract [en]

    In this paper we address the problem of solving parity games over the configuration graphs of bounded phase multi-pushdown systems. A non-elementary decision procedure was proposed for this problem by A. Seth. In this paper, we provide a simple and inductive construction to solve this problem. We also prove a non-elementary lower-bound, answering a question posed by A. Seth.

  • 41.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    LIAFA, CNRS and University of Paris Diderot.
    Kumar, K. Narayan
    Chennai Mathematical Institute, Chennai, India.
    Saivasan, Prakash
    TU Braunschweig, Germany.
    Verification of Asynchronous Programs with Nested Locks2017In: 37th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science, FSTTCS 2017, December 11-15, 2017, Kanpur, India / [ed] Satya Lokam and R. Ramanujam, Dagstuhl, Germany, 2017, Vol. 93, p. 11:1-11:14Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider asynchronous programs consisting of multiple recursive threads running in parallel. Each of the threads is equipped with a multi-set. The threads can create tasks and post them onto the multi-sets or read a task from their own. In addition, they can synchronise through a finite set of locks. In this paper, we show that the reachability problem for such class of asynchronous programs is undecidable even under the nested locking policy. We then show that the reachability problem becomes decidable (Exp-space-complete) when the locks are not allowed to be held across tasks. Finally, we show that the problem is NP-complete when in addition to previous restrictions, threads always read tasks from the same state.

  • 42.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Chistikov, Dmitry
    Max Planck Inst Software Syst MPI SWS, Kaiserslautern, Germany..
    Hofman, Piotr
    Univ Paris Saclay, CNRS, LSV, St Aubin, France.;Univ Paris Saclay, ENS Cachan, St Aubin, France..
    Kumar, K. Narayan
    Chennai Math Inst, Madras, Tamil Nadu, India..
    Saivasan, Prakash
    Chennai Math Inst, Madras, Tamil Nadu, India.;Univ Kaiserslautern, Kaiserslautern, Germany..
    Zetzsche, Georg
    Univ Paris Saclay, CNRS, LSV, St Aubin, France.;Univ Paris Saclay, ENS Cachan, St Aubin, France..
    The complexity of regular abstractions of one-counter languages2016In: Proceedings Of The 31St Annual ACM-IEEE Symposium On Logic In Computer Science (LICS 2016), 2016, p. 207-216Conference paper (Refereed)
    Abstract [en]

    We study the computational and descriptional complexity of the following transformation: Given a one-counter automaton (OCA) A, construct a nondeterministic finite automaton (NFA) B that recognizes an abstraction of the language L (A) : its (1) downward closure, (2) upward closure, or (3) Parikh image. For the Parikh image over a fixed alphabet and for the upward and downward closures, we find polynomial-time algorithms that compute such an NFA. For the Parikh image with the alphabet as part of the input, we find a quasi-polynomial time algorithm and prove a completeness result: we construct a sequence of OCA that admits a polynomial-time algorithm iff there is one for all OCA. For all three abstractions, it was previously unknown whether appropriate NFA of sub-exponential size exist.

  • 43.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Kumar, K. Narayan
    Saivasan, Prakash
    Acceleration in Multi-PushDown Systems2016In: Tools and Algorithms for the Construction and Analysis of Systems, Springer, 2016, p. 698-714Conference paper (Refereed)
  • 44.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Meyer, Roland
    TU Braunschweig, Germany.
    Muskalla, Sebastian
    TU Braunschweig, Germany.
    Saivasan, Prakash
    TU Braunschweig, Germany.
    On the Upward/Downward Closures of Petri Nets∗2017In: 42nd International Symposium on Mathematical Foundations of Computer Science (MFCS 2017) / [ed] Kim G. Larsen and Hans L. Bodlaender and Jean-Francois Raskin, Dagstuhl, Germany, 2017, Vol. 83, p. 49:1-49:14Conference paper (Refereed)
    Abstract [en]

    We study the size and the complexity of computing finite state automata (FSA) representing and approximating the downward and the upward closure of Petri net languages with coverability as the acceptance condition. We show how to construct an FSA recognizing the upward closure of a Petri net language in doubly-exponential time, and therefore the size is at most doubly exponential. For downward closures, we prove that the size of the minimal automata can be non-primitive recursive. In the case of BPP nets, a well-known subclass of Petri nets, we show that an FSA accepting the downward/upward closure can be constructed in exponential time. Furthermore, we consider the problem of checking whether a simple regular language is included in the downward/upward closure of a Petri net/BPP net language. We show that this problem is EXPSPACE-complete (resp. NP-complete) in the case of Petri nets (resp. BPP nets). Finally, we show that it is decidable whether a Petri net language is upward/downward closed.

  • 45.
    Aziz Abdulla, Parosh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Aiswarya, C.
    Chennai Mathematical Institute .
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Data Multi-Pushdown Automata2017In: The 28th International Conference on Concurrency Theory, CONCUR 2017, September 5-8, 2017, Berlin, Germany / [ed] Roland Meyer and Uwe Nestmann, Dagstuhl, Germany, 2017, Vol. 85, p. 38:1-38:17Conference paper (Refereed)
    Abstract [en]

    We extend the classical model of multi-pushdown systems by considering systems that operate on a finite set of variables ranging over natural numbers. The conditions on variables are defined via gap-order constraints that allow to compare variables for equality, or to check that the gap between the values of two variables exceeds a given natural number. Furthermore, each message inside a stack is equipped with a data item representing its value. When a message is pushed to the stack, its value may be defined by a variable. When a message is popped, its value may be copied to a variable. Thus, we obtain a system that is infinite in multiple dimensions, namely we have a number of stacks that may contain an unbounded number of messages each of which is equipped with a natural number. It is well-known that the verification of any non-trivial property of multi-pushdown systems is undecidable, even for two stacks and for a finite data-domain. In this paper, we show the decidability of the reachability problem for the classes of data multi-pushdown system that admit a bounded split-width (or equivalently a bounded tree-width). As an immediate consequence, we obtain decidability for several subclasses of data multi-pushdown systems. These include systems with single stacks, restricted ordering policies on stack operations, bounded scope, bounded phase, and bounded context switches.

  • 46.
    Backeman, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    New techniques for handling quantifiers in Boolean and first-order logic2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The automation of reasoning has been an aim of research for a long time. Already in 17th century, the famous mathematician Leibniz invented a mechanical calculator capable of performing all four basic arithmetic operators. Although automatic reasoning can be done in different fields, many of the procedures for automated reasoning handles formulas of first-order logic. Examples of use cases includes hardware verification, program analysis and knowledge representation.

    One of the fundamental challenges in first-order logic is handling quantifiers and the equality predicate. On the one hand, SMT-solvers (Satisfiability Modulo Theories) are quite efficient at dealing with theory reasoning, on the other hand they have limited support for complete and efficient reasoning with quantifiers. Sequent, tableau and resolution calculi are methods which are used to construct proofs for first-order formulas and can use more efficient techniques to handle quantifiers. Unfortunately, in contrast to SMT, handling theories is more difficult.

    In this thesis we investigate methods to handle quantifiers by restricting search spaces to finite domains which can be explored in a systematic manner. We present this approach in two different contexts.

    First we introduce a function synthesis based on template-based quantifier elimination, which is applied to gene interaction computation. The function synthesis is shown to be capable of generating smaller representations of solutions than previous solvers, and by restricting the constructed functions to certain forms we can produce formulas which can more easily be interpreted by a biologist.

    Secondly we introduce the concept of Bounded Rigid E-Unification (BREU), a finite form of unification that can be used to define a complete and sound sequent calculus for first-order logic with equality. We show how to solve this bounded form of unification in an efficient manner, yielding a first-order theorem prover utilizing BREU that is competitive with other state-of-the-art tableau theorem provers.

  • 47.
    Backeman, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Dunn, Sara-Jane
    Yordanov, Boyan
    Wintersteiger, Christoph M.
    Algebraic polynomial-based synthesis for abstract Boolean network analysis2016In: Satisfiability Modulo Theories: SMT 2016, RWTH Aachen University , 2016, p. 41-50Conference paper (Refereed)
  • 48.
    Backeman, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rümmer, Philipp
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Efficient algorithms for bounded rigid E-unification2015In: Automated Reasoning with Analytic Tableaux and Related Methods, Springer, 2015, p. 70-85Conference paper (Refereed)
  • 49.
    Backeman, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rümmer, Philipp
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Free variables and theories: Revisiting rigid E-unification2015In: Frontiers of Combining Systems, Springer, 2015, p. 3-13Conference paper (Refereed)
  • 50.
    Backeman, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rümmer, Philipp
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Theorem proving with bounded rigid E-unification2015In: Automated Deduction – CADE-25, Springer, 2015, p. 572-587Conference paper (Refereed)
123456 1 - 50 of 267
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