@inproceedings{7348,
abstract = {The monitoring of event frequencies can be used to recognize behavioral anomalies, to identify trends, and to deduce or discard hypotheses about the underlying system. For example, the performance of a web server may be monitored based on the ratio of the total count of requests from the least and most active clients. Exact frequency monitoring, however, can be prohibitively expensive; in the above example it would require as many counters as there are clients. In this paper, we propose the efficient probabilistic monitoring of common frequency properties, including the mode (i.e., the most common event) and the median of an event sequence. We define a logic to express composite frequency properties as a combination of atomic frequency properties. Our main contribution is an algorithm that, under suitable probabilistic assumptions, can be used to monitor these important frequency properties with four counters, independent of the number of different events. Our algorithm samples longer and longer subwords of an infinite event sequence. We prove the almost-sure convergence of our algorithm by generalizing ergodic theory from increasing-length prefixes to increasing-length subwords of an infinite sequence. A similar algorithm could be used to learn a connected Markov chain of a given structure from observing its outputs, to arbitrary precision, for a given confidence. },
author = {Ferrere, Thomas and Henzinger, Thomas A and Kragl, Bernhard},
booktitle = {28th EACSL Annual Conference on Computer Science Logic},
isbn = {9783959771320},
issn = {1868-8969},
location = {Barcelona, Spain},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Monitoring event frequencies}},
doi = {10.4230/LIPIcs.CSL.2020.20},
volume = {152},
year = {2020},
}
@inproceedings{8012,
abstract = {Asynchronous programs are notoriously difficult to reason about because they spawn computation tasks which take effect asynchronously in a nondeterministic way. Devising inductive invariants for such programs requires understanding and stating complex relationships between an unbounded number of computation tasks in arbitrarily long executions. In this paper, we introduce inductive sequentialization, a new proof rule that sidesteps this complexity via a sequential reduction, a sequential program that captures every behavior of the original program up to reordering of coarse-grained commutative actions. A sequential reduction of a concurrent program is easy to reason about since it corresponds to a simple execution of the program in an idealized synchronous environment, where processes act in a fixed order and at the same speed. We have implemented and integrated our proof rule in the CIVL verifier, allowing us to provably derive fine-grained implementations of asynchronous programs. We have successfully applied our proof rule to a diverse set of message-passing protocols, including leader election protocols, two-phase commit, and Paxos.},
author = {Kragl, Bernhard and Enea, Constantin and Henzinger, Thomas A and Mutluergil, Suha Orhun and Qadeer, Shaz},
booktitle = {Proceedings of the 41st ACM SIGPLAN Conference on Programming Language Design and Implementation},
isbn = {9781450376136},
location = {London, United Kingdom},
pages = {227--242},
publisher = {Association for Computing Machinery},
title = {{Inductive sequentialization of asynchronous programs}},
doi = {10.1145/3385412.3385980},
year = {2020},
}
@article{7426,
abstract = {This paper presents a novel abstraction technique for analyzing Lyapunov and asymptotic stability of polyhedral switched systems. A polyhedral switched system is a hybrid system in which the continuous dynamics is specified by polyhedral differential inclusions, the invariants and guards are specified by polyhedral sets and the switching between the modes do not involve reset of variables. A finite state weighted graph abstracting the polyhedral switched system is constructed from a finite partition of the state–space, such that the satisfaction of certain graph conditions, such as the absence of cycles with product of weights on the edges greater than (or equal) to 1, implies the stability of the system. However, the graph is in general conservative and hence, the violation of the graph conditions does not imply instability. If the analysis fails to establish stability due to the conservativeness in the approximation, a counterexample (cycle with product of edge weights greater than or equal to 1) indicating a potential reason for the failure is returned. Further, a more precise approximation of the switched system can be constructed by considering a finer partition of the state–space in the construction of the finite weighted graph. We present experimental results on analyzing stability of switched systems using the above method.},
author = {Garcia Soto, Miriam and Prabhakar, Pavithra},
issn = {1751570X},
journal = {Nonlinear Analysis: Hybrid Systems},
number = {5},
publisher = {Elsevier},
title = {{Abstraction based verification of stability of polyhedral switched systems}},
doi = {10.1016/j.nahs.2020.100856},
volume = {36},
year = {2020},
}
@article{6761,
abstract = {In resource allocation games, selfish players share resources that are needed in order to fulfill their objectives. The cost of using a resource depends on the load on it. In the traditional setting, the players make their choices concurrently and in one-shot. That is, a strategy for a player is a subset of the resources. We introduce and study dynamic resource allocation games. In this setting, the game proceeds in phases. In each phase each player chooses one resource. A scheduler dictates the order in which the players proceed in a phase, possibly scheduling several players to proceed concurrently. The game ends when each player has collected a set of resources that fulfills his objective. The cost for each player then depends on this set as well as on the load on the resources in it – we consider both congestion and cost-sharing games. We argue that the dynamic setting is the suitable setting for many applications in practice. We study the stability of dynamic resource allocation games, where the appropriate notion of stability is that of subgame perfect equilibrium, study the inefficiency incurred due to selfish behavior, and also study problems that are particular to the dynamic setting, like constraints on the order in which resources can be chosen or the problem of finding a scheduler that achieves stability.},
author = {Avni, Guy and Henzinger, Thomas A and Kupferman, Orna},
issn = {03043975},
journal = {Theoretical Computer Science},
pages = {42--55},
publisher = {Elsevier},
title = {{Dynamic resource allocation games}},
doi = {10.1016/j.tcs.2019.06.031},
volume = {807},
year = {2020},
}
@inproceedings{7505,
abstract = {Neural networks have demonstrated unmatched performance in a range of classification tasks. Despite numerous efforts of the research community, novelty detection remains one of the significant limitations of neural networks. The ability to identify previously unseen inputs as novel is crucial for our understanding of the decisions made by neural networks. At runtime, inputs not falling into any of the categories learned during training cannot be classified correctly by the neural network. Existing approaches treat the neural network as a black box and try to detect novel inputs based on the confidence of the output predictions. However, neural networks are not trained to reduce their confidence for novel inputs, which limits the effectiveness of these approaches. We propose a framework to monitor a neural network by observing the hidden layers. We employ a common abstraction from program analysis - boxes - to identify novel behaviors in the monitored layers, i.e., inputs that cause behaviors outside the box. For each neuron, the boxes range over the values seen in training. The framework is efficient and flexible to achieve a desired trade-off between raising false warnings and detecting novel inputs. We illustrate the performance and the robustness to variability in the unknown classes on popular image-classification benchmarks.},
author = {Henzinger, Thomas A and Lukina, Anna and Schilling, Christian},
booktitle = {24th European Conference on Artificial Intelligence},
location = {Santiago de Compostela, Spain},
title = {{Outside the box: Abstraction-based monitoring of neural networks}},
year = {2020},
}
@inproceedings{7808,
abstract = {Quantization converts neural networks into low-bit fixed-point computations which can be carried out by efficient integer-only hardware, and is standard practice for the deployment of neural networks on real-time embedded devices. However, like their real-numbered counterpart, quantized networks are not immune to malicious misclassification caused by adversarial attacks. We investigate how quantization affects a network’s robustness to adversarial attacks, which is a formal verification question. We show that neither robustness nor non-robustness are monotonic with changing the number of bits for the representation and, also, neither are preserved by quantization from a real-numbered network. For this reason, we introduce a verification method for quantized neural networks which, using SMT solving over bit-vectors, accounts for their exact, bit-precise semantics. We built a tool and analyzed the effect of quantization on a classifier for the MNIST dataset. We demonstrate that, compared to our method, existing methods for the analysis of real-numbered networks often derive false conclusions about their quantizations, both when determining robustness and when detecting attacks, and that existing methods for quantized networks often miss attacks. Furthermore, we applied our method beyond robustness, showing how the number of bits in quantization enlarges the gender bias of a predictor for students’ grades.},
author = {Giacobbe, Mirco and Henzinger, Thomas A and Lechner, Mathias},
booktitle = {International Conference on Tools and Algorithms for the Construction and Analysis of Systems},
isbn = {9783030452360},
issn = {16113349},
location = {Dublin, Ireland},
pages = {79--97},
publisher = {Springer Nature},
title = {{How many bits does it take to quantize your neural network?}},
doi = {10.1007/978-3-030-45237-7_5},
volume = {12079},
year = {2020},
}
@phdthesis{6894,
abstract = {Hybrid automata combine finite automata and dynamical systems, and model the interaction of digital with physical systems. Formal analysis that can guarantee the safety of all behaviors or rigorously witness failures, while unsolvable in general, has been tackled algorithmically using, e.g., abstraction, bounded model-checking, assisted theorem proving.
Nevertheless, very few methods have addressed the time-unbounded reachability analysis of hybrid automata and, for current sound and automatic tools, scalability remains critical. We develop methods for the polyhedral abstraction of hybrid automata, which construct coarse overapproximations and tightens them incrementally, in a CEGAR fashion. We use template polyhedra, i.e., polyhedra whose facets are normal to a given set of directions.
While, previously, directions were given by the user, we introduce (1) the first method
for computing template directions from spurious counterexamples, so as to generalize and
eliminate them. The method applies naturally to convex hybrid automata, i.e., hybrid
automata with (possibly non-linear) convex constraints on derivatives only, while for linear
ODE requires further abstraction. Specifically, we introduce (2) the conic abstractions,
which, partitioning the state space into appropriate (possibly non-uniform) cones, divide
curvy trajectories into relatively straight sections, suitable for polyhedral abstractions.
Finally, we introduce (3) space-time interpolation, which, combining interval arithmetic
and template refinement, computes appropriate (possibly non-uniform) time partitioning
and template directions along spurious trajectories, so as to eliminate them.
We obtain sound and automatic methods for the reachability analysis over dense
and unbounded time of convex hybrid automata and hybrid automata with linear ODE.
We build prototype tools and compare—favorably—our methods against the respective
state-of-the-art tools, on several benchmarks.},
author = {Giacobbe, Mirco},
issn = {2663-337X},
pages = {132},
publisher = {IST Austria},
title = {{Automatic time-unbounded reachability analysis of hybrid systems}},
doi = {10.15479/AT:ISTA:6894},
year = {2019},
}
@inproceedings{6565,
abstract = {In this paper, we address the problem of synthesizing periodic switching controllers for stabilizing a family of linear systems. Our broad approach consists of constructing a finite game graph based on the family of linear systems such that every winning strategy on the game graph corresponds to a stabilizing switching controller for the family of linear systems. The construction of a (finite) game graph, the synthesis of a winning strategy and the extraction of a stabilizing controller are all computationally feasible. We illustrate our method on an example.},
author = {Kundu, Atreyee and Garcia Soto, Miriam and Prabhakar, Pavithra},
booktitle = {5th Indian Control Conference Proceedings},
isbn = {978-153866246-5},
location = {Delhi, India},
publisher = {IEEE},
title = {{Formal synthesis of stabilizing controllers for periodically controlled linear switched systems}},
doi = {10.1109/INDIANCC.2019.8715598},
year = {2019},
}
@inproceedings{6042,
abstract = {Static program analyzers are increasingly effective in checking correctness properties of programs and reporting any errors found, often in the form of error traces. However, developers still spend a significant amount of time on debugging. This involves processing long error traces in an effort to localize a bug to a relatively small part of the program and to identify its cause. In this paper, we present a technique for automated fault localization that, given a program and an error trace, efficiently narrows down the cause of the error to a few statements. These statements are then ranked in terms of their suspiciousness. Our technique relies only on the semantics of the given program and does not require any test cases or user guidance. In experiments on a set of C benchmarks, we show that our technique is effective in quickly isolating the cause of error while out-performing other state-of-the-art fault-localization techniques.},
author = {Christakis, Maria and Heizmann, Matthias and Mansur, Muhammad Numair and Schilling, Christian and Wüstholz, Valentin},
booktitle = {25th International Conference on Tools and Algorithms for the Construction and Analysis of Systems },
location = {Prague, Czech Republic},
pages = {226--243},
publisher = {Springer Nature},
title = {{Semantic fault localization and suspiciousness ranking}},
doi = {10.1007/978-3-030-17462-0_13},
volume = {11427},
year = {2019},
}
@inproceedings{6888,
abstract = {In this paper, we design novel liquid time-constant recurrent neural networks for robotic control, inspired by the brain of the nematode, C. elegans. In the worm's nervous system, neurons communicate through nonlinear time-varying synaptic links established amongst them by their particular wiring structure. This property enables neurons to express liquid time-constants dynamics and therefore allows the network to originate complex behaviors with a small number of neurons. We identify neuron-pair communication motifs as design operators and use them to configure compact neuronal network structures to govern sequential robotic tasks. The networks are systematically designed to map the environmental observations to motor actions, by their hierarchical topology from sensory neurons, through recurrently-wired interneurons, to motor neurons. The networks are then parametrized in a supervised-learning scheme by a search-based algorithm. We demonstrate that obtained networks realize interpretable dynamics. We evaluate their performance in controlling mobile and arm robots, and compare their attributes to other artificial neural network-based control agents. Finally, we experimentally show their superior resilience to environmental noise, compared to the existing machine learning-based methods.},
author = {Lechner, Mathias and Hasani, Ramin and Zimmer, Manuel and Henzinger, Thomas A and Grosu, Radu},
booktitle = {Proceedings - IEEE International Conference on Robotics and Automation},
isbn = {9781538660270},
location = {Montreal, QC, Canada},
publisher = {IEEE},
title = {{Designing worm-inspired neural networks for interpretable robotic control}},
doi = {10.1109/icra.2019.8793840},
volume = {2019-May},
year = {2019},
}
@inproceedings{6035,
abstract = {We present JuliaReach, a toolbox for set-based reachability analysis of dynamical systems. JuliaReach consists of two main packages: Reachability, containing implementations of reachability algorithms for continuous and hybrid systems, and LazySets, a standalone library that implements state-of-the-art algorithms for calculus with convex sets. The library offers both concrete and lazy set representations, where the latter stands for the ability to delay set computations until they are needed. The choice of the programming language Julia and the accompanying documentation of our toolbox allow researchers to easily translate set-based algorithms from mathematics to software in a platform-independent way, while achieving runtime performance that is comparable to statically compiled languages. Combining lazy operations in high dimensions and explicit computations in low dimensions, JuliaReach can be applied to solve complex, large-scale problems.},
author = {Bogomolov, Sergiy and Forets, Marcelo and Frehse, Goran and Potomkin, Kostiantyn and Schilling, Christian},
booktitle = {Proceedings of the 22nd International Conference on Hybrid Systems: Computation and Control},
isbn = {9781450362825},
keyword = {reachability analysis, hybrid systems, lazy computation},
location = {Montreal, QC, Canada},
pages = {39--44},
publisher = {ACM},
title = {{JuliaReach: A toolbox for set-based reachability}},
doi = {10.1145/3302504.3311804},
volume = {22},
year = {2019},
}
@inproceedings{7576,
abstract = {We present the results of a friendly competition for formal verification of continuous and hybrid systems with nonlinear continuous dynamics. The friendly competition took place as part of the workshop Applied Verification for Continuous and Hybrid Systems (ARCH) in 2019. In this year, 6 tools Ariadne, CORA, DynIbex, Flow*, Isabelle/HOL, and JuliaReach (in alphabetic order) participated. They are applied to solve reachability analysis problems on four benchmark problems, one of them with hybrid dynamics. We do not rank the tools based on the results, but show the current status and discover the potential advantages of different tools.},
author = {Immler, Fabian and Althoff, Matthias and Benet, Luis and Chapoutot, Alexandre and Chen, Xin and Forets, Marcelo and Geretti, Luca and Kochdumper, Niklas and Sanders, David P. and Schilling, Christian},
booktitle = {EPiC Series in Computing},
issn = {23987340},
location = {Montreal, Canada},
pages = {41--61},
publisher = {EasyChair Publications},
title = {{ARCH-COMP19 Category Report: Continuous and hybrid systems with nonlinear dynamics}},
doi = {10.29007/m75b},
volume = {61},
year = {2019},
}
@inproceedings{6985,
abstract = {In this paper, we introduce a novel method to interpret recurrent neural networks (RNNs), particularly long short-term memory networks (LSTMs) at the cellular level. We propose a systematic pipeline for interpreting individual hidden state dynamics within the network using response characterization methods. The ranked contribution of individual cells to the network's output is computed by analyzing a set of interpretable metrics of their decoupled step and sinusoidal responses. As a result, our method is able to uniquely identify neurons with insightful dynamics, quantify relationships between dynamical properties and test accuracy through ablation analysis, and interpret the impact of network capacity on a network's dynamical distribution. Finally, we demonstrate the generalizability and scalability of our method by evaluating a series of different benchmark sequential datasets.},
author = {Hasani, Ramin and Amini, Alexander and Lechner, Mathias and Naser, Felix and Grosu, Radu and Rus, Daniela},
booktitle = {Proceedings of the International Joint Conference on Neural Networks},
isbn = {9781728119854},
location = {Budapest, Hungary},
publisher = {IEEE},
title = {{Response characterization for auditing cell dynamics in long short-term memory networks}},
doi = {10.1109/ijcnn.2019.8851954},
year = {2019},
}
@inproceedings{6428,
abstract = {Safety and security are major concerns in the development of Cyber-Physical Systems (CPS). Signal temporal logic (STL) was proposedas a language to specify and monitor the correctness of CPS relativeto formalized requirements. Incorporating STL into a developmentprocess enables designers to automatically monitor and diagnosetraces, compute robustness estimates based on requirements, andperform requirement falsification, leading to productivity gains inverification and validation activities; however, in its current formSTL is agnostic to the input/output classification of signals, andthis negatively impacts the relevance of the analysis results.In this paper we propose to make the interface explicit in theSTL language by introducing input/output signal declarations. Wethen define new measures of input vacuity and output robustnessthat better reflect the nature of the system and the specification in-tent. The resulting framework, which we call interface-aware signaltemporal logic (IA-STL), aids verification and validation activities.We demonstrate the benefits of IA-STL on several CPS analysisactivities: (1) robustness-driven sensitivity analysis, (2) falsificationand (3) fault localization. We describe an implementation of our en-hancement to STL and associated notions of robustness and vacuityin a prototype extension of Breach, a MATLAB®/Simulink®toolboxfor CPS verification and validation. We explore these methodologi-cal improvements and evaluate our results on two examples fromthe automotive domain: a benchmark powertrain control systemand a hydrogen fuel cell system.},
author = {Ferrere, Thomas and Nickovic, Dejan and Donzé, Alexandre and Ito, Hisahiro and Kapinski, James},
booktitle = {Proceedings of the 2019 22nd ACM International Conference on Hybrid Systems: Computation and Control},
isbn = {9781450362825},
location = {Montreal, Canada},
pages = {57--66},
publisher = {ACM},
title = {{Interface-aware signal temporal logic}},
doi = {10.1145/3302504.3311800},
year = {2019},
}
@inproceedings{6822,
abstract = {In two-player games on graphs, the players move a token through a graph to produce an infinite path, which determines the qualitative winner or quantitative payoff of the game. In bidding games, in each turn, we hold an auction between the two players to determine which player moves the token. Bidding games have largely been studied with concrete bidding mechanisms that are variants of a first-price auction: in each turn both players simultaneously submit bids, the higher
bidder moves the token, and pays his bid to the lower bidder in Richman bidding, to the bank in poorman bidding, and in taxman bidding, the bid is split between the other player and the bank according to a predefined constant factor. Bidding games are deterministic games. They have an intriguing connection with a fragment of stochastic games called
randomturn games. We study, for the first time, a combination of bidding games with probabilistic behavior; namely, we study bidding games that are played on Markov decision processes, where the players bid for the right to choose the next action, which determines the probability distribution according to which the next vertex is chosen. We study parity and meanpayoff bidding games on MDPs and extend results from the deterministic bidding setting to the probabilistic one.},
author = {Avni, Guy and Henzinger, Thomas A and Ibsen-Jensen, Rasmus and Novotny, Petr},
booktitle = { Proceedings of the 13th International Conference of Reachability Problems},
isbn = {978-303030805-6},
issn = {0302-9743},
location = {Brussels, Belgium},
pages = {1--12},
publisher = {Springer},
title = {{Bidding games on Markov decision processes}},
doi = {10.1007/978-3-030-30806-3_1},
volume = {11674},
year = {2019},
}
@inproceedings{6884,
abstract = {In two-player games on graphs, the players move a token through a graph to produce a finite or infinite path, which determines the qualitative winner or quantitative payoff of the game. We study bidding games in which the players bid for the right to move the token. Several bidding rules were studied previously. In Richman bidding, in each round, the players simultaneously submit bids, and the higher bidder moves the token and pays the other player. Poorman bidding is similar except that the winner of the bidding pays the "bank" rather than the other player. Taxman bidding spans the spectrum between Richman and poorman bidding. They are parameterized by a constant tau in [0,1]: portion tau of the winning bid is paid to the other player, and portion 1-tau to the bank. While finite-duration (reachability) taxman games have been studied before, we present, for the first time, results on infinite-duration taxman games. It was previously shown that both Richman and poorman infinite-duration games with qualitative objectives reduce to reachability games, and we show a similar result here. Our most interesting results concern quantitative taxman games, namely mean-payoff games, where poorman and Richman bidding differ significantly. A central quantity in these games is the ratio between the two players' initial budgets. While in poorman mean-payoff games, the optimal payoff of a player depends on the initial ratio, in Richman bidding, the payoff depends only on the structure of the game. In both games the optimal payoffs can be found using (different) probabilistic connections with random-turn games in which in each turn, instead of bidding, a coin is tossed to determine which player moves. While the value with Richman bidding equals the value of a random-turn game with an un-biased coin, with poorman bidding, the bias in the coin is the initial ratio of the budgets. We give a complete classification of mean-payoff taxman games that is based on a probabilistic connection: the value of a taxman bidding game with parameter tau and initial ratio r, equals the value of a random-turn game that uses a coin with bias F(tau, r) = (r+tau * (1-r))/(1+tau). Thus, we show that Richman bidding is the exception; namely, for every tau <1, the value of the game depends on the initial ratio. Our proof technique simplifies and unifies the previous proof techniques for both Richman and poorman bidding. },
author = {Avni, Guy and Henzinger, Thomas A and Zikelic, Dorde},
location = {Aachen, Germany},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Bidding mechanisms in graph games}},
doi = {10.4230/LIPICS.MFCS.2019.11},
volume = {138},
year = {2019},
}
@article{7109,
abstract = {We show how to construct temporal testers for the logic MITL, a prominent linear-time logic for real-time systems. A temporal tester is a transducer that inputs a signal holding the Boolean value of atomic propositions and outputs the truth value of a formula along time. Here we consider testers over continuous-time Boolean signals that use clock variables to enforce duration constraints, as in timed automata. We first rewrite the MITL formula into a “simple” formula using a limited set of temporal modalities. We then build testers for these specific modalities and show how to compose testers for simple formulae into complex ones. Temporal testers can be turned into acceptors, yielding a compositional translation from MITL to timed automata. This construction is much simpler than previously known and remains asymptotically optimal. It supports both past and future operators and can easily be extended.},
author = {Ferrere, Thomas and Maler, Oded and Ničković, Dejan and Pnueli, Amir},
issn = {0004-5411},
journal = {Journal of the ACM},
number = {3},
publisher = {ACM},
title = {{From real-time logic to timed automata}},
doi = {10.1145/3286976},
volume = {66},
year = {2019},
}
@inproceedings{7147,
abstract = {The expression of a gene is characterised by its transcription factors and the function processing them. If the transcription factors are not affected by gene products, the regulating function is often represented as a combinational logic circuit, where the outputs (product) are determined by current input values (transcription factors) only, and are hence independent on their relative arrival times. However, the simultaneous arrival of transcription factors (TFs) in genetic circuits is a strong assumption, given that the processes of transcription and translation of a gene into a protein introduce intrinsic time delays and that there is no global synchronisation among the arrival times of different molecular species at molecular targets.
In this paper, we construct an experimentally implementable genetic circuit with two inputs and a single output, such that, in presence of small delays in input arrival, the circuit exhibits qualitatively distinct observable phenotypes. In particular, these phenotypes are long lived transients: they all converge to a single value, but so slowly, that they seem stable for an extended time period, longer than typical experiment duration. We used rule-based language to prototype our circuit, and we implemented a search for finding the parameter combinations raising the phenotypes of interest.
The behaviour of our prototype circuit has wide implications. First, it suggests that GRNs can exploit event timing to create phenotypes. Second, it opens the possibility that GRNs are using event timing to react to stimuli and memorise events, without explicit feedback in regulation. From the modelling perspective, our prototype circuit demonstrates the critical importance of analysing the transient dynamics at the promoter binding sites of the DNA, before applying rapid equilibrium assumptions.},
author = {Guet, Calin C and Henzinger, Thomas A and Igler, Claudia and Petrov, Tatjana and Sezgin, Ali},
booktitle = {17th International Conference on Computational Methods in Systems Biology},
isbn = {9783030313036},
issn = {1611-3349},
location = {Trieste, Italy},
pages = {155--187},
publisher = {Springer Nature},
title = {{Transient memory in gene regulation}},
doi = {10.1007/978-3-030-31304-3_9},
volume = {11773},
year = {2019},
}
@inproceedings{7159,
abstract = {Cyber-physical systems (CPS) and the Internet-of-Things (IoT) result in a tremendous amount of generated, measured and recorded time-series data. Extracting temporal segments that encode patterns with useful information out of these huge amounts of data is an extremely difficult problem. We propose shape expressions as a declarative formalism for specifying, querying and extracting sophisticated temporal patterns from possibly noisy data. Shape expressions are regular expressions with arbitrary (linear, exponential, sinusoidal, etc.) shapes with parameters as atomic predicates and additional constraints on these parameters. We equip shape expressions with a novel noisy semantics that combines regular expression matching semantics with statistical regression. We characterize essential properties of the formalism and propose an efficient approximate shape expression matching procedure. We demonstrate the wide applicability of this technique on two case studies. },
author = {Ničković, Dejan and Qin, Xin and Ferrere, Thomas and Mateis, Cristinel and Deshmukh, Jyotirmoy},
booktitle = {19th International Conference on Runtime Verification},
isbn = {9783030320782},
issn = {0302-9743},
location = {Porto, Portugal},
pages = {292--309},
publisher = {Springer Nature},
title = {{Shape expressions for specifying and extracting signal features}},
doi = {10.1007/978-3-030-32079-9_17},
volume = {11757},
year = {2019},
}
@inproceedings{7231,
abstract = {Piecewise Barrier Tubes (PBT) is a new technique for flowpipe overapproximation for nonlinear systems with polynomial dynamics, which leverages a combination of barrier certificates. PBT has advantages over traditional time-step based methods in dealing with those nonlinear dynamical systems in which there is a large difference in speed between trajectories, producing an overapproximation that is time independent. However, the existing approach for PBT is not efficient due to the application of interval methods for enclosure-box computation, and it can only deal with continuous dynamical systems without uncertainty. In this paper, we extend the approach with the ability to handle both continuous and hybrid dynamical systems with uncertainty that can reside in parameters and/or noise. We also improve the efficiency of the method significantly, by avoiding the use of interval-based methods for the enclosure-box computation without loosing soundness. We have developed a C++ prototype implementing the proposed approach and we evaluate it on several benchmarks. The experiments show that our approach is more efficient and precise than other methods in the literature.},
author = {Kong, Hui and Bartocci, Ezio and Jiang, Yu and Henzinger, Thomas A},
booktitle = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)},
isbn = {9783030296612},
issn = {16113349},
location = {Amsterdam, The Netherlands},
pages = {123--141},
publisher = {Springer Nature},
title = {{Piecewise robust barrier tubes for nonlinear hybrid systems with uncertainty}},
doi = {10.1007/978-3-030-29662-9_8},
volume = {11750},
year = {2019},
}
@article{6752,
abstract = {Two-player games on graphs are widely studied in formal methods, as they model the interaction between a system and its environment. The game is played by moving a token throughout a graph to produce an infinite path. There are several common modes to determine how the players move the token through the graph; e.g., in turn-based games the players alternate turns in moving the token. We study the bidding mode of moving the token, which, to the best of our knowledge, has never been studied in infinite-duration games. The following bidding rule was previously defined and called Richman bidding. Both players have separate budgets, which sum up to 1. In each turn, a bidding takes place: Both players submit bids simultaneously, where a bid is legal if it does not exceed the available budget, and the higher bidder pays his bid to the other player and moves the token. The central question studied in bidding games is a necessary and sufficient initial budget for winning the game: a threshold budget in a vertex is a value t ∈ [0, 1] such that if Player 1’s budget exceeds t, he can win the game; and if Player 2’s budget exceeds 1 − t, he can win the game. Threshold budgets were previously shown to exist in every vertex of a reachability game, which have an interesting connection with random-turn games—a sub-class of simple stochastic games in which the player who moves is chosen randomly. We show the existence of threshold budgets for a qualitative class of infinite-duration games, namely parity games, and a quantitative class, namely mean-payoff games. The key component of the proof is a quantitative solution to strongly connected mean-payoff bidding games in which we extend the connection with random-turn games to these games, and construct explicit optimal strategies for both players.},
author = {Avni, Guy and Henzinger, Thomas A and Chonev, Ventsislav K},
issn = {1557735X},
journal = {Journal of the ACM},
number = {4},
publisher = {ACM},
title = {{Infinite-duration bidding games}},
doi = {10.1145/3340295},
volume = {66},
year = {2019},
}
@inproceedings{6462,
abstract = {A controller is a device that interacts with a plant. At each time point,it reads the plant’s state and issues commands with the goal that the plant oper-ates optimally. Constructing optimal controllers is a fundamental and challengingproblem. Machine learning techniques have recently been successfully applied totrain controllers, yet they have limitations. Learned controllers are monolithic andhard to reason about. In particular, it is difficult to add features without retraining,to guarantee any level of performance, and to achieve acceptable performancewhen encountering untrained scenarios. These limitations can be addressed bydeploying quantitative run-timeshieldsthat serve as a proxy for the controller.At each time point, the shield reads the command issued by the controller andmay choose to alter it before passing it on to the plant. We show how optimalshields that interfere as little as possible while guaranteeing a desired level ofcontroller performance, can be generated systematically and automatically usingreactive synthesis. First, we abstract the plant by building a stochastic model.Second, we consider the learned controller to be a black box. Third, we mea-surecontroller performanceandshield interferenceby two quantitative run-timemeasures that are formally defined using weighted automata. Then, the problemof constructing a shield that guarantees maximal performance with minimal inter-ference is the problem of finding an optimal strategy in a stochastic2-player game“controller versus shield” played on the abstract state space of the plant with aquantitative objective obtained from combining the performance and interferencemeasures. We illustrate the effectiveness of our approach by automatically con-structing lightweight shields for learned traffic-light controllers in various roadnetworks. The shields we generate avoid liveness bugs, improve controller per-formance in untrained and changing traffic situations, and add features to learnedcontrollers, such as giving priority to emergency vehicles.},
author = {Avni, Guy and Bloem, Roderick and Chatterjee, Krishnendu and Henzinger, Thomas A and Konighofer, Bettina and Pranger, Stefan},
booktitle = {31st International Conference on Computer-Aided Verification},
isbn = {9783030255398},
issn = {0302-9743},
location = {New York, NY, United States},
pages = {630--649},
publisher = {Springer},
title = {{Run-time optimization for learned controllers through quantitative games}},
doi = {10.1007/978-3-030-25540-4_36},
volume = {11561},
year = {2019},
}
@inproceedings{6493,
abstract = {We present two algorithmic approaches for synthesizing linear hybrid automata from experimental data. Unlike previous approaches, our algorithms work without a template and generate an automaton with nondeterministic guards and invariants, and with an arbitrary number and topology of modes. They thus construct a succinct model from the data and provide formal guarantees. In particular, (1) the generated automaton can reproduce the data up to a specified tolerance and (2) the automaton is tight, given the first guarantee. Our first approach encodes the synthesis problem as a logical formula in the theory of linear arithmetic, which can then be solved by an SMT solver. This approach minimizes the number of modes in the resulting model but is only feasible for limited data sets. To address scalability, we propose a second approach that does not enforce to find a minimal model. The algorithm constructs an initial automaton and then iteratively extends the automaton based on processing new data. Therefore the algorithm is well-suited for online and synthesis-in-the-loop applications. The core of the algorithm is a membership query that checks whether, within the specified tolerance, a given data set can result from the execution of a given automaton. We solve this membership problem for linear hybrid automata by repeated reachability computations. We demonstrate the effectiveness of the algorithm on synthetic data sets and on cardiac-cell measurements.},
author = {Garcia Soto, Miriam and Henzinger, Thomas A and Schilling, Christian and Zeleznik, Luka},
booktitle = {31st International Conference on Computer-Aided Verification},
isbn = {9783030255398},
issn = {0302-9743},
keyword = {Synthesis, Linear hybrid automaton, Membership},
location = {New York City, NY, USA},
pages = {297--314},
publisher = {Springer},
title = {{Membership-based synthesis of linear hybrid automata}},
doi = {10.1007/978-3-030-25540-4_16},
volume = {11561},
year = {2019},
}
@inproceedings{6885,
abstract = {A vector addition system with states (VASS) consists of a finite set of states and counters. A configuration is a state and a value for each counter; a transition changes the state and each counter is incremented, decremented, or left unchanged. While qualitative properties such as state and configuration reachability have been studied for VASS, we consider the long-run average cost of infinite computations of VASS. The cost of a configuration is for each state, a linear combination of the counter values. In the special case of uniform cost functions, the linear combination is the same for all states. The (regular) long-run emptiness problem is, given a VASS, a cost function, and a threshold value, if there is a (lasso-shaped) computation such that the long-run average value of the cost function does not exceed the threshold. For uniform cost functions, we show that the regular long-run emptiness problem is (a) decidable in polynomial time for integer-valued VASS, and (b) decidable but nonelementarily hard for natural-valued VASS (i.e., nonnegative counters). For general cost functions, we show that the problem is (c) NP-complete for integer-valued VASS, and (d) undecidable for natural-valued VASS. Our most interesting result is for (c) integer-valued VASS with general cost functions, where we establish a connection between the regular long-run emptiness problem and quadratic Diophantine inequalities. The general (nonregular) long-run emptiness problem is equally hard as the regular problem in all cases except (c), where it remains open. },
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
location = {Amsterdam, Netherlands},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Long-run average behavior of vector addition systems with states}},
doi = {10.4230/LIPICS.CONCUR.2019.27},
volume = {140},
year = {2019},
}
@inproceedings{7232,
abstract = {We present Mixed-time Signal Temporal Logic (STL−MX), a specification formalism which extends STL by capturing the discrete/ continuous time duality found in many cyber-physical systems (CPS), as well as mixed-signal electronic designs. In STL−MX, properties of components with continuous dynamics are expressed in STL, while specifications of components with discrete dynamics are written in LTL. To combine the two layers, we evaluate formulas on two traces, discrete- and continuous-time, and introduce two interface operators that map signals, properties and their satisfaction signals across the two time domains. We show that STL-mx has the expressive power of STL supplemented with an implicit T-periodic clock signal. We develop and implement an algorithm for monitoring STL-mx formulas and illustrate the approach using a mixed-signal example. },
author = {Ferrere, Thomas and Maler, Oded and Nickovic, Dejan},
booktitle = {Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)},
isbn = {9783030296612},
issn = {16113349},
location = {Amsterdam, The Netherlands},
pages = {59--75},
publisher = {Springer Nature},
title = {{Mixed-time signal temporal logic}},
doi = {10.1007/978-3-030-29662-9_4},
volume = {11750},
year = {2019},
}
@inproceedings{7453,
abstract = {We illustrate the ingredients of the state-of-the-art of model-based approach for the formal design and verification of cyber-physical systems. To capture the interaction between a discrete controller and its continuously evolving environment, we use the formal models of timed and hybrid automata. We explain the steps of modeling and verification in the tools Uppaal and SpaceEx using a case study based on a dual-chamber implantable pacemaker monitoring a human heart. We show how to design a model as a composition of components, how to construct models at varying levels of detail, how to establish that one model is an abstraction of another, how to specify correctness requirements using temporal logic, and how to verify that a model satisfies a logical requirement.},
author = {Alur, Rajeev and Giacobbe, Mirco and Henzinger, Thomas A and Larsen, Kim G. and Mikučionis, Marius},
booktitle = {Computing and Software Science},
isbn = {9783319919072},
issn = {0302-9743},
pages = {452--477},
publisher = {Springer Nature},
title = {{Continuous-time models for system design and analysis}},
doi = {10.1007/978-3-319-91908-9_22},
volume = {10000},
year = {2019},
}
@inproceedings{6886,
abstract = {In two-player games on graphs, the players move a token through a graph to produce an infinite path, which determines the winner of the game. Such games are central in formal methods since they model the interaction between a non-terminating system and its environment. In bidding games the players bid for the right to move the token: in each round, the players simultaneously submit bids, and the higher bidder moves the token and pays the other player. Bidding games are known to have a clean and elegant mathematical structure that relies on the ability of the players to submit arbitrarily small bids. Many applications, however, require a fixed granularity for the bids, which can represent, for example, the monetary value expressed in cents. We study, for the first time, the combination of discrete-bidding and infinite-duration games. Our most important result proves that these games form a large determined subclass of concurrent games, where determinacy is the strong property that there always exists exactly one player who can guarantee winning the game. In particular, we show that, in contrast to non-discrete bidding games, the mechanism with which tied bids are resolved plays an important role in discrete-bidding games. We study several natural tie-breaking mechanisms and show that, while some do not admit determinacy, most natural mechanisms imply determinacy for every pair of initial budgets. },
author = {Aghajohari, Milad and Avni, Guy and Henzinger, Thomas A},
location = {Amsterdam, Netherlands},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Determinacy in discrete-bidding infinite-duration games}},
doi = {10.4230/LIPICS.CONCUR.2019.20},
volume = {140},
year = {2019},
}
@inproceedings{299,
abstract = {We introduce in this paper AMT 2.0 , a tool for qualitative and quantitative analysis of hybrid continuous and Boolean signals that combine numerical values and discrete events. The evaluation of the signals is based on rich temporal specifications expressed in extended Signal Temporal Logic (xSTL), which integrates Timed Regular Expressions (TRE) within Signal Temporal Logic (STL). The tool features qualitative monitoring (property satisfaction checking), trace diagnostics for explaining and justifying property violations and specification-driven measurement of quantitative features of the signal.},
author = {Nickovic, Dejan and Lebeltel, Olivier and Maler, Oded and Ferrere, Thomas and Ulus, Dogan},
editor = {Beyer, Dirk and Huisman, Marieke},
location = {Thessaloniki, Greece},
pages = {303 -- 319},
publisher = {Springer},
title = {{AMT 2.0: Qualitative and quantitative trace analysis with extended signal temporal logic}},
doi = {10.1007/978-3-319-89963-3_18},
volume = {10806},
year = {2018},
}
@article{434,
abstract = {In this paper, we present a formal model-driven design approach to establish a safety-assured implementation of multifunction vehicle bus controller (MVBC), which controls the data transmission among the devices of the vehicle. First, the generic models and safety requirements described in International Electrotechnical Commission Standard 61375 are formalized as time automata and timed computation tree logic formulas, respectively. With model checking tool Uppaal, we verify whether or not the constructed timed automata satisfy the formulas and several logic inconsistencies in the original standard are detected and corrected. Then, we apply the code generation tool Times to generate C code from the verified model, which is later synthesized into a real MVBC chip, with some handwriting glue code. Furthermore, the runtime verification tool RMOR is applied on the integrated code, to verify some safety requirements that cannot be formalized on the timed automata. For evaluation, we compare the proposed approach with existing MVBC design methods, such as BeagleBone, Galsblock, and Simulink. Experiments show that more ambiguousness or bugs in the standard are detected during Uppaal verification, and the generated code of Times outperforms the C code generated by others in terms of the synthesized binary code size. The errors in the standard have been confirmed and the resulting MVBC has been deployed in the real train communication network.},
author = {Jiang, Yu and Liu, Han and Song, Huobing and Kong, Hui and Wang, Rui and Guan, Yong and Sha, Lui},
journal = {IEEE Transactions on Intelligent Transportation Systems},
number = {10},
pages = {3320 -- 3333},
publisher = {IEEE},
title = {{Safety-assured model-driven design of the multifunction vehicle bus controller}},
doi = {10.1109/TITS.2017.2778077},
volume = {19},
year = {2018},
}
@inproceedings{5788,
abstract = {In two-player games on graphs, the players move a token through a graph to produce an infinite path, which determines the winner or payoff of the game. Such games are central in formal verification since they model the interaction between a non-terminating system and its environment. We study bidding games in which the players bid for the right to move the token. Two bidding rules have been defined. In Richman bidding, in each round, the players simultaneously submit bids, and the higher bidder moves the token and pays the other player. Poorman bidding is similar except that the winner of the bidding pays the “bank” rather than the other player. While poorman reachability games have been studied before, we present, for the first time, results on infinite-duration poorman games. A central quantity in these games is the ratio between the two players’ initial budgets. The questions we study concern a necessary and sufficient ratio with which a player can achieve a goal. For reachability objectives, such threshold ratios are known to exist for both bidding rules. We show that the properties of poorman reachability games extend to complex qualitative objectives such as parity, similarly to the Richman case. Our most interesting results concern quantitative poorman games, namely poorman mean-payoff games, where we construct optimal strategies depending on the initial ratio, by showing a connection with random-turn based games. The connection in itself is interesting, because it does not hold for reachability poorman games. We also solve the complexity problems that arise in poorman bidding games.},
author = {Avni, Guy and Henzinger, Thomas A and Ibsen-Jensen, Rasmus},
isbn = {9783030046118},
issn = {03029743},
location = {Oxford, UK},
pages = {21--36},
publisher = {Springer},
title = {{Infinite-duration poorman-bidding games}},
doi = {10.1007/978-3-030-04612-5_2},
volume = {11316},
year = {2018},
}
@inproceedings{78,
abstract = {We provide a procedure for detecting the sub-segments of an incrementally observed Boolean signal ω that match a given temporal pattern ϕ. As a pattern specification language, we use timed regular expressions, a formalism well-suited for expressing properties of concurrent asynchronous behaviors embedded in metric time. We construct a timed automaton accepting the timed language denoted by ϕ and modify it slightly for the purpose of matching. We then apply zone-based reachability computation to this automaton while it reads ω, and retrieve all the matching segments from the results. Since the procedure is automaton based, it can be applied to patterns specified by other formalisms such as timed temporal logics reducible to timed automata or directly encoded as timed automata. The procedure has been implemented and its performance on synthetic examples is demonstrated.},
author = {Bakhirkin, Alexey and Ferrere, Thomas and Nickovic, Dejan and Maler, Oded and Asarin, Eugene},
isbn = {978-3-030-00150-6},
location = {Bejing, China},
pages = {215 -- 232},
publisher = {Springer},
title = {{Online timed pattern matching using automata}},
doi = {10.1007/978-3-030-00151-3_13},
volume = {11022},
year = {2018},
}
@inproceedings{5959,
abstract = {Formalizing properties of systems with continuous dynamics is a challenging task. In this paper, we propose a formal framework for specifying and monitoring rich temporal properties of real-valued signals. We introduce signal first-order logic (SFO) as a specification language that combines first-order logic with linear-real arithmetic and unary function symbols interpreted as piecewise-linear signals. We first show that while the satisfiability problem for SFO is undecidable, its membership and monitoring problems are decidable. We develop an offline monitoring procedure for SFO that has polynomial complexity in the size of the input trace and the specification, for a fixed number of quantifiers and function symbols. We show that the algorithm has computation time linear in the size of the input trace for the important fragment of bounded-response specifications interpreted over input traces with finite variability. We can use our results to extend signal temporal logic with first-order quantifiers over time and value parameters, while preserving its efficient monitoring. We finally demonstrate the practical appeal of our logic through a case study in the micro-electronics domain.},
author = {Bakhirkin, Alexey and Ferrere, Thomas and Henzinger, Thomas A and Nickovicl, Deian},
booktitle = {2018 International Conference on Embedded Software},
isbn = {9781538655603},
location = {Turin, Italy},
pages = {1--10},
publisher = {IEEE},
title = {{Keynote: The first-order logic of signals}},
doi = {10.1109/emsoft.2018.8537203},
year = {2018},
}
@inproceedings{144,
abstract = {The task of a monitor is to watch, at run-time, the execution of a reactive system, and signal the occurrence of a safety violation in the observed sequence of events. While finite-state monitors have been studied extensively, in practice, monitoring software also makes use of unbounded memory. We define a model of automata equipped with integer-valued registers which can execute only a bounded number of instructions between consecutive events, and thus can form the theoretical basis for the study of infinite-state monitors. We classify these register monitors according to the number k of available registers, and the type of register instructions. In stark contrast to the theory of computability for register machines, we prove that for every k 1, monitors with k + 1 counters (with instruction set 〈+1, =〉) are strictly more expressive than monitors with k counters. We also show that adder monitors (with instruction set 〈1, +, =〉) are strictly more expressive than counter monitors, but are complete for monitoring all computable safety -languages for k = 6. Real-time monitors are further required to signal the occurrence of a safety violation as soon as it occurs. The expressiveness hierarchy for counter monitors carries over to real-time monitors. We then show that 2 adders cannot simulate 3 counters in real-time. Finally, we show that real-time adder monitors with inequalities are as expressive as real-time Turing machines.},
author = {Ferrere, Thomas and Henzinger, Thomas A and Saraç, Ege},
location = {Oxford, UK},
pages = {394 -- 403},
publisher = {IEEE},
title = {{A theory of register monitors}},
doi = {10.1145/3209108.3209194},
volume = {Part F138033},
year = {2018},
}
@inproceedings{156,
abstract = {Imprecision in timing can sometimes be beneficial: Metric interval temporal logic (MITL), disabling the expression of punctuality constraints, was shown to translate to timed automata, yielding an elementary decision procedure. We show how this principle extends to other forms of dense-time specification using regular expressions. By providing a clean, automaton-based formal framework for non-punctual languages, we are able to recover and extend several results in timed systems. Metric interval regular expressions (MIRE) are introduced, providing regular expressions with non-singular duration constraints. We obtain that MIRE are expressively complete relative to a class of one-clock timed automata, which can be determinized using additional clocks. Metric interval dynamic logic (MIDL) is then defined using MIRE as temporal modalities. We show that MIDL generalizes known extensions of MITL, while translating to timed automata at comparable cost.},
author = {Ferrere, Thomas},
location = {Oxford, UK},
pages = {147 -- 164},
publisher = {Springer},
title = {{The compound interest in relaxing punctuality}},
doi = {10.1007/978-3-319-95582-7_9},
volume = {10951},
year = {2018},
}
@inproceedings{24,
abstract = {Partially-observable Markov decision processes (POMDPs) with discounted-sum payoff are a standard framework to model a wide range of problems related to decision making under uncertainty. Traditionally, the goal has been to obtain policies that optimize the expectation of the discounted-sum payoff. A key drawback of the expectation measure is that even low probability events with extreme payoff can significantly affect the expectation, and thus the obtained policies are not necessarily risk-averse. An alternate approach is to optimize the probability that the payoff is above a certain threshold, which allows obtaining risk-averse policies, but ignores optimization of the expectation. We consider the expectation optimization with probabilistic guarantee (EOPG) problem, where the goal is to optimize the expectation ensuring that the payoff is above a given threshold with at least a specified probability. We present several results on the EOPG problem, including the first algorithm to solve it.},
author = {Chatterjee, Krishnendu and Elgyütt, Adrian and Novotny, Petr and Rouillé, Owen},
location = {Stockholm, Sweden},
pages = {4692 -- 4699},
publisher = {IJCAI},
title = {{Expectation optimization with probabilistic guarantees in POMDPs with discounted-sum objectives}},
doi = {10.24963/ijcai.2018/652},
volume = {2018},
year = {2018},
}
@inbook{86,
abstract = {Responsiveness—the requirement that every request to a system be eventually handled—is one of the fundamental liveness properties of a reactive system. Average response time is a quantitative measure for the responsiveness requirement used commonly in performance evaluation. We show how average response time can be computed on state-transition graphs, on Markov chains, and on game graphs. In all three cases, we give polynomial-time algorithms.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
booktitle = {Principles of Modeling},
editor = {Lohstroh, Marten and Derler, Patricia and Sirjani, Marjan},
pages = {143 -- 161},
publisher = {Springer},
title = {{Computing average response time}},
doi = {10.1007/978-3-319-95246-8_9},
volume = {10760},
year = {2018},
}
@inproceedings{81,
abstract = {We solve the offline monitoring problem for timed propositional temporal logic (TPTL), interpreted over dense-time Boolean signals. The variant of TPTL we consider extends linear temporal logic (LTL) with clock variables and reset quantifiers, providing a mechanism to specify real-time constraints. We first describe a general monitoring algorithm based on an exhaustive computation of the set of satisfying clock assignments as a finite union of zones. We then propose a specialized monitoring algorithm for the one-variable case using a partition of the time domain based on the notion of region equivalence, whose complexity is linear in the length of the signal, thereby generalizing a known result regarding the monitoring of metric temporal logic (MTL). The region and zone representations of time constraints are known from timed automata verification and can also be used in the discrete-time case. Our prototype implementation appears to outperform previous discrete-time implementations of TPTL monitoring,},
author = {Elgyütt, Adrian and Ferrere, Thomas and Henzinger, Thomas A},
location = {Beijing, China},
pages = {53 -- 70},
publisher = {Springer},
title = {{Monitoring temporal logic with clock variables}},
doi = {10.1007/978-3-030-00151-3_4},
volume = {11022},
year = {2018},
}
@inproceedings{79,
abstract = {Markov Decision Processes (MDPs) are a popular class of models suitable for solving control decision problems in probabilistic reactive systems. We consider parametric MDPs (pMDPs) that include parameters in some of the transition probabilities to account for stochastic uncertainties of the environment such as noise or input disturbances. We study pMDPs with reachability objectives where the parameter values are unknown and impossible to measure directly during execution, but there is a probability distribution known over the parameter values. We study for the first time computing parameter-independent strategies that are expectation optimal, i.e., optimize the expected reachability probability under the probability distribution over the parameters. We present an encoding of our problem to partially observable MDPs (POMDPs), i.e., a reduction of our problem to computing optimal strategies in POMDPs. We evaluate our method experimentally on several benchmarks: a motivating (repeated) learner model; a series of benchmarks of varying configurations of a robot moving on a grid; and a consensus protocol.},
author = {Arming, Sebastian and Bartocci, Ezio and Chatterjee, Krishnendu and Katoen, Joost P and Sokolova, Ana},
location = {Beijing, China},
pages = {53--70},
publisher = {Springer},
title = {{Parameter-independent strategies for pMDPs via POMDPs}},
doi = {10.1007/978-3-319-99154-2_4},
volume = {11024},
year = {2018},
}
@inproceedings{182,
abstract = {We describe a new algorithm for the parametric identification problem for signal temporal logic (STL), stated as follows. Given a densetime real-valued signal w and a parameterized temporal logic formula φ, compute the subset of the parameter space that renders the formula satisfied by the signal. Unlike previous solutions, which were based on search in the parameter space or quantifier elimination, our procedure works recursively on φ and computes the evolution over time of the set of valid parameter assignments. This procedure is similar to that of monitoring or computing the robustness of φ relative to w. Our implementation and experiments demonstrate that this approach can work well in practice.},
author = {Bakhirkin, Alexey and Ferrere, Thomas and Maler, Oded},
booktitle = {Proceedings of the 21st International Conference on Hybrid Systems},
isbn = {978-1-4503-5642-8 },
location = {Porto, Portugal},
pages = {177 -- 186},
publisher = {ACM},
title = {{Efficient parametric identification for STL}},
doi = {10.1145/3178126.3178132},
year = {2018},
}
@inproceedings{133,
abstract = {Synchronous programs are easy to specify because the side effects of an operation are finished by the time the invocation of the operation returns to the caller. Asynchronous programs, on the other hand, are difficult to specify because there are side effects due to pending computation scheduled as a result of the invocation of an operation. They are also difficult to verify because of the large number of possible interleavings of concurrent computation threads. We present synchronization, a new proof rule that simplifies the verification of asynchronous programs by introducing the fiction, for proof purposes, that asynchronous operations complete synchronously. Synchronization summarizes an asynchronous computation as immediate atomic effect. Modular verification is enabled via pending asynchronous calls in atomic summaries, and a complementary proof rule that eliminates pending asynchronous calls when components and their specifications are composed. We evaluate synchronization in the context of a multi-layer refinement verification methodology on a collection of benchmark programs.},
author = {Kragl, Bernhard and Qadeer, Shaz and Henzinger, Thomas A},
issn = {18688969},
location = {Beijing, China},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Synchronizing the asynchronous}},
doi = {10.4230/LIPIcs.CONCUR.2018.21},
volume = {118},
year = {2018},
}
@inproceedings{140,
abstract = {Reachability analysis is difficult for hybrid automata with affine differential equations, because the reach set needs to be approximated. Promising abstraction techniques usually employ interval methods or template polyhedra. Interval methods account for dense time and guarantee soundness, and there are interval-based tools that overapproximate affine flowpipes. But interval methods impose bounded and rigid shapes, which make refinement expensive and fixpoint detection difficult. Template polyhedra, on the other hand, can be adapted flexibly and can be unbounded, but sound template refinement for unbounded reachability analysis has been implemented only for systems with piecewise constant dynamics. We capitalize on the advantages of both techniques, combining interval arithmetic and template polyhedra, using the former to abstract time and the latter to abstract space. During a CEGAR loop, whenever a spurious error trajectory is found, we compute additional space constraints and split time intervals, and use these space-time interpolants to eliminate the counterexample. Space-time interpolation offers a lazy, flexible framework for increasing precision while guaranteeing soundness, both for error avoidance and fixpoint detection. To the best of out knowledge, this is the first abstraction refinement scheme for the reachability analysis over unbounded and dense time of affine hybrid systems, which is both sound and automatic. We demonstrate the effectiveness of our algorithm with several benchmark examples, which cannot be handled by other tools.},
author = {Frehse, Goran and Giacobbe, Mirco and Henzinger, Thomas A},
issn = {03029743},
location = {Oxford, United Kingdom},
pages = {468 -- 486},
publisher = {Springer},
title = {{Space-time interpolants}},
doi = {10.1007/978-3-319-96145-3_25},
volume = {10981},
year = {2018},
}
@inproceedings{183,
abstract = {Fault-localization is considered to be a very tedious and time-consuming activity in the design of complex Cyber-Physical Systems (CPS). This laborious task essentially requires expert knowledge of the system in order to discover the cause of the fault. In this context, we propose a new procedure that AIDS designers in debugging Simulink/Stateflow hybrid system models, guided by Signal Temporal Logic (STL) specifications. The proposed method relies on three main ingredients: (1) a monitoring and a trace diagnostics procedure that checks whether a tested behavior satisfies or violates an STL specification, localizes time segments and interfaces variables contributing to the property violations; (2) a slicing procedure that maps these observable behavior segments to the internal states and transitions of the Simulink model; and (3) a spectrum-based fault-localization method that combines the previous analysis from multiple tests to identify the internal states and/or transitions that are the most likely to explain the fault. We demonstrate the applicability of our approach on two Simulink models from the automotive and the avionics domain.},
author = {Bartocci, Ezio and Ferrere, Thomas and Manjunath, Niveditha and Nickovic, Dejan},
location = {Porto, Portugal},
pages = {197 -- 206},
publisher = {Association for Computing Machinery, Inc},
title = {{Localizing faults in simulink/stateflow models with STL}},
doi = {10.1145/3178126.3178131},
year = {2018},
}
@inproceedings{6005,
abstract = {Network games are widely used as a model for selfish resource-allocation problems. In the classicalmodel, each player selects a path connecting her source and target vertices. The cost of traversingan edge depends on theload; namely, number of players that traverse it. Thus, it abstracts the factthat different users may use a resource at different times and for different durations, which playsan important role in determining the costs of the users in reality. For example, when transmittingpackets in a communication network, routing traffic in a road network, or processing a task in aproduction system, actual sharing and congestion of resources crucially depends on time.In [13], we introducedtimed network games, which add a time component to network games.Each vertexvin the network is associated with a cost function, mapping the load onvto theprice that a player pays for staying invfor one time unit with this load. Each edge in thenetwork is guarded by the time intervals in which it can be traversed, which forces the players tospend time in the vertices. In this work we significantly extend the way time can be referred toin timed network games. In the model we study, the network is equipped withclocks, and, as intimed automata, edges are guarded by constraints on the values of the clocks, and their traversalmay involve a reset of some clocks. We argue that the stronger model captures many realisticnetworks. The addition of clocks breaks the techniques we developed in [13] and we developnew techniques in order to show that positive results on classic network games carry over to thestronger timed setting.},
author = {Avni, Guy and Guha, Shibashis and Kupferman, Orna},
location = {Liverpool, United Kingdom},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Timed network games with clocks}},
doi = {10.4230/LIPICS.MFCS.2018.23},
volume = {117},
year = {2018},
}
@article{5677,
abstract = {Recently, contract-based design has been proposed as an “orthogonal” approach that complements system design methodologies proposed so far to cope with the complexity of system design. Contract-based design provides a rigorous scaffolding for verification, analysis, abstraction/refinement, and even synthesis. A number of results have been obtained in this domain but a unified treatment of the topic that can help put contract-based design in perspective was missing. This monograph intends to provide such a treatment where contracts are precisely defined and characterized so that they can be used in design methodologies with no ambiguity. In particular, this monograph identifies the essence of complex system design using contracts through a mathematical “meta-theory”, where all the properties of the methodology are derived from a very abstract and generic notion of contract. We show that the meta-theory provides deep and illuminating links with existing contract and interface theories, as well as guidelines for designing new theories. Our study encompasses contracts for both software and systems, with emphasis on the latter. We illustrate the use of contracts with two examples: requirement engineering for a parking garage management, and the development of contracts for timing and scheduling in the context of the Autosar methodology in use in the automotive sector.},
author = {Benveniste, Albert and Nickovic, Dejan and Caillaud, Benoît and Passerone, Roberto and Raclet, Jean Baptiste and Reinkemeier, Philipp and Sangiovanni-Vincentelli, Alberto and Damm, Werner and Henzinger, Thomas A and Larsen, Kim G.},
issn = {15513939},
journal = {Foundations and Trends in Electronic Design Automation},
number = {2-3},
pages = {124--400},
publisher = {Now Publishers Inc},
title = {{Contracts for system design}},
doi = {10.1561/1000000053},
volume = {12},
year = {2018},
}
@book{3300,
abstract = {This book first explores the origins of this idea, grounded in theoretical work on temporal logic and automata. The editors and authors are among the world's leading researchers in this domain, and they contributed 32 chapters representing a thorough view of the development and application of the technique. Topics covered include binary decision diagrams, symbolic model checking, satisfiability modulo theories, partial-order reduction, abstraction, interpolation, concurrency, security protocols, games, probabilistic model checking, and process algebra, and chapters on the transfer of theory to industrial practice, property specification languages for hardware, and verification of real-time systems and hybrid systems.
The book will be valuable for researchers and graduate students engaged with the development of formal methods and verification tools.},
author = {Clarke, Edmund M. and Henzinger, Thomas A and Veith, Helmut and Bloem, Roderick},
publisher = {Springer},
title = {{Handbook of model checking}},
doi = {10.1007/978-3-319-10575-8},
year = {2018},
}
@inproceedings{160,
abstract = {We present layered concurrent programs, a compact and expressive notation for specifying refinement proofs of concurrent programs. A layered concurrent program specifies a sequence of connected concurrent programs, from most concrete to most abstract, such that common parts of different programs are written exactly once. These programs are expressed in the ordinary syntax of imperative concurrent programs using gated atomic actions, sequencing, choice, and (recursive) procedure calls. Each concurrent program is automatically extracted from the layered program. We reduce refinement to the safety of a sequence of concurrent checker programs, one each to justify the connection between every two consecutive concurrent programs. These checker programs are also automatically extracted from the layered program. Layered concurrent programs have been implemented in the CIVL verifier which has been successfully used for the verification of several complex concurrent programs.},
author = {Kragl, Bernhard and Qadeer, Shaz},
location = {Oxford, UK},
pages = {79 -- 102},
publisher = {Springer},
title = {{Layered Concurrent Programs}},
doi = {10.1007/978-3-319-96145-3_5},
volume = {10981},
year = {2018},
}
@inproceedings{297,
abstract = {Graph games played by two players over finite-state graphs are central in many problems in computer science. In particular, graph games with ω -regular winning conditions, specified as parity objectives, which can express properties such as safety, liveness, fairness, are the basic framework for verification and synthesis of reactive systems. The decisions for a player at various states of the graph game are represented as strategies. While the algorithmic problem for solving graph games with parity objectives has been widely studied, the most prominent data-structure for strategy representation in graph games has been binary decision diagrams (BDDs). However, due to the bit-level representation, BDDs do not retain the inherent flavor of the decisions of strategies, and are notoriously hard to minimize to obtain succinct representation. In this work we propose decision trees for strategy representation in graph games. Decision trees retain the flavor of decisions of strategies and allow entropy-based minimization to obtain succinct trees. However, decision trees work in settings (e.g., probabilistic models) where errors are allowed, and overfitting of data is typically avoided. In contrast, for strategies in graph games no error is allowed, and the decision tree must represent the entire strategy. We develop new techniques to extend decision trees to overcome the above obstacles, while retaining the entropy-based techniques to obtain succinct trees. We have implemented our techniques to extend the existing decision tree solvers. We present experimental results for problems in reactive synthesis to show that decision trees provide a much more efficient data-structure for strategy representation as compared to BDDs.},
author = {Brázdil, Tomáš and Chatterjee, Krishnendu and Kretinsky, Jan and Toman, Viktor},
location = {Thessaloniki, Greece},
pages = {385 -- 407},
publisher = {Springer},
title = {{Strategy representation by decision trees in reactive synthesis}},
doi = {10.1007/978-3-319-89960-2_21},
volume = {10805},
year = {2018},
}
@article{6006,
abstract = {Network games (NGs) are played on directed graphs and are extensively used in network design and analysis. Search problems for NGs include finding special strategy profiles such as a Nash equilibrium and a globally-optimal solution. The networks modeled by NGs may be huge. In formal verification, abstraction has proven to be an extremely effective technique for reasoning about systems with big and even infinite state spaces. We describe an abstraction-refinement methodology for reasoning about NGs. Our methodology is based on an abstraction function that maps the state space of an NG to a much smaller state space. We search for a global optimum and a Nash equilibrium by reasoning on an under- and an over-approximation defined on top of this smaller state space. When the approximations are too coarse to find such profiles, we refine the abstraction function. We extend the abstraction-refinement methodology to labeled networks, where the objectives of the players are regular languages. Our experimental results demonstrate the effectiveness of the methodology. },
author = {Avni, Guy and Guha, Shibashis and Kupferman, Orna},
issn = {2073-4336},
journal = {Games},
number = {3},
publisher = {MDPI AG},
title = {{An abstraction-refinement methodology for reasoning about network games}},
doi = {10.3390/g9030039},
volume = {9},
year = {2018},
}
@article{608,
abstract = {Synthesis is the automated construction of a system from its specification. In real life, hardware and software systems are rarely constructed from scratch. Rather, a system is typically constructed from a library of components. Lustig and Vardi formalized this intuition and studied LTL synthesis from component libraries. In real life, designers seek optimal systems. In this paper we add optimality considerations to the setting. We distinguish between quality considerations (for example, size - the smaller a system is, the better it is), and pricing (for example, the payment to the company who manufactured the component). We study the problem of designing systems with minimal quality-cost and price. A key point is that while the quality cost is individual - the choices of a designer are independent of choices made by other designers that use the same library, pricing gives rise to a resource-allocation game - designers that use the same component share its price, with the share being proportional to the number of uses (a component can be used several times in a design). We study both closed and open settings, and in both we solve the problem of finding an optimal design. In a setting with multiple designers, we also study the game-theoretic problems of the induced resource-allocation game.},
author = {Avni, Guy and Kupferman, Orna},
journal = {Theoretical Computer Science},
pages = {50 -- 72},
publisher = {Elsevier},
title = {{Synthesis from component libraries with costs}},
doi = {10.1016/j.tcs.2017.11.001},
volume = {712},
year = {2018},
}
@inbook{60,
abstract = {Model checking is a computer-assisted method for the analysis of dynamical systems that can be modeled by state-transition systems. Drawing from research traditions in mathematical logic, programming languages, hardware design, and theoretical computer science, model checking is now widely used for the verification of hardware and software in industry. This chapter is an introduction and short survey of model checking. The chapter aims to motivate and link the individual chapters of the handbook, and to provide context for readers who are not familiar with model checking.},
author = {Clarke, Edmund and Henzinger, Thomas A and Veith, Helmut},
booktitle = {Handbook of Model Checking},
editor = {Henzinger, Thomas A},
pages = {1 -- 26},
publisher = {Springer},
title = {{Introduction to model checking}},
doi = {10.1007/978-3-319-10575-8_1},
year = {2018},
}