@inproceedings{2217,
abstract = {As hybrid systems involve continuous behaviors, they should be evaluated by quantitative methods, rather than qualitative methods. In this paper we adapt a quantitative framework, called model measuring, to the hybrid systems domain. The model-measuring problem asks, given a model M and a specification, what is the maximal distance such that all models within that distance from M satisfy (or violate) the specification. A distance function on models is given as part of the input of the problem. Distances, especially related to continuous behaviors are more natural in the hybrid case than the discrete case. We are interested in distances represented by monotonic hybrid automata, a hybrid counterpart of (discrete) weighted automata, whose recognized timed languages are monotone (w.r.t. inclusion) in the values of parameters.
The contributions of this paper are twofold. First, we give sufficient conditions under which the model-measuring problem can be solved. Second, we discuss the modeling of distances and applications of the model-measuring problem.},
author = {Henzinger, Thomas A and Otop, Jan},
booktitle = {Proceedings of the 17th international conference on Hybrid systems: computation and control},
location = {Berlin, Germany},
pages = {213 -- 222},
publisher = {Springer},
title = {{Model measuring for hybrid systems}},
doi = {10.1145/2562059.2562130},
year = {2014},
}
@article{2233,
abstract = { A discounted-sum automaton (NDA) is a nondeterministic finite automaton with edge weights, valuing a run by the discounted sum of visited edge weights. More precisely, the weight in the i-th position of the run is divided by λi, where the discount factor λ is a fixed rational number greater than 1. The value of a word is the minimal value of the automaton runs on it. Discounted summation is a common and useful measuring scheme, especially for infinite sequences, reflecting the assumption that earlier weights are more important than later weights. Unfortunately, determinization of NDAs, which is often essential in formal verification, is, in general, not possible. We provide positive news, showing that every NDA with an integral discount factor is determinizable. We complete the picture by proving that the integers characterize exactly the discount factors that guarantee determinizability: for every nonintegral rational discount factor λ, there is a nondeterminizable λ-NDA. We also prove that the class of NDAs with integral discount factors enjoys closure under the algebraic operations min, max, addition, and subtraction, which is not the case for general NDAs nor for deterministic NDAs. For general NDAs, we look into approximate determinization, which is always possible as the influence of a word's suffix decays. We show that the naive approach, of unfolding the automaton computations up to a sufficient level, is doubly exponential in the discount factor. We provide an alternative construction for approximate determinization, which is singly exponential in the discount factor, in the precision, and in the number of states. We also prove matching lower bounds, showing that the exponential dependency on each of these three parameters cannot be avoided. All our results hold equally for automata over finite words and for automata over infinite words. },
author = {Boker, Udi and Henzinger, Thomas A},
issn = {18605974},
journal = {Logical Methods in Computer Science},
number = {1},
publisher = {International Federation of Computational Logic},
title = {{Exact and approximate determinization of discounted-sum automata}},
doi = {10.2168/LMCS-10(1:10)2014},
volume = {10},
year = {2014},
}
@inproceedings{2239,
abstract = {The analysis of the energy consumption of software is an important goal for quantitative formal methods. Current methods, using weighted transition systems or energy games, model the energy source as an ideal resource whose status is characterized by one number, namely the amount of remaining energy. Real batteries, however, exhibit behaviors that can deviate substantially from an ideal energy resource. Based on a discretization of a standard continuous battery model, we introduce battery transition systems. In this model, a battery is viewed as consisting of two parts-the available-charge tank and the bound-charge tank. Any charge or discharge is applied to the available-charge tank. Over time, the energy from each tank diffuses to the other tank. Battery transition systems are infinite state systems that, being not well-structured, fall into no decidable class that is known to us. Nonetheless, we are able to prove that the !-regular modelchecking problem is decidable for battery transition systems. We also present a case study on the verification of control programs for energy-constrained semi-autonomous robots.},
author = {Boker, Udi and Henzinger, Thomas A and Radhakrishna, Arjun},
isbn = {978-145032544-8},
location = {San Diego, USA},
number = {1},
pages = {595 -- 606},
publisher = {ACM},
title = {{Battery transition systems}},
doi = {10.1145/2535838.2535875},
volume = {49},
year = {2014},
}
@misc{5411,
abstract = {Model-based testing is a promising technology for black-box software and hardware testing, in which test cases are generated automatically from high-level specifications. Nowadays, systems typically consist of multiple interacting components and, due to their complexity, testing presents a considerable portion of the effort and cost in the design process. Exploiting the compositional structure of system specifications can considerably reduce the effort in model-based testing. Moreover, inferring properties about the system from testing its individual components allows the designer to reduce the amount of integration testing.
In this paper, we study compositional properties of the IOCO-testing theory. We propose a new approach to composition and hiding operations, inspired by contract-based design and interface theories. These operations preserve behaviors that are compatible under composition and hiding, and prune away incompatible ones. The resulting specification characterizes the input sequences for which the unit testing of components is sufficient to infer the correctness of component integration without the need for further tests. We provide a methodology that uses these results to minimize integration testing effort, but also to detect potential weaknesses in specifications. While we focus on asynchronous models and the IOCO conformance relation, the resulting methodology can be applied to a broader class of systems.},
author = {Daca, Przemyslaw and Henzinger, Thomas A and Krenn, Willibald and Nickovic, Dejan},
issn = {2664-1690},
pages = {20},
publisher = {IST Austria},
title = {{Compositional specifications for IOCO testing}},
doi = {10.15479/AT:IST-2014-148-v2-1},
year = {2014},
}
@misc{5415,
abstract = {Recently there has been a significant effort to add quantitative properties in formal verification and synthesis. While weighted automata over finite and infinite words provide a natural and flexible framework to express quantitative properties, perhaps surprisingly, several basic system properties such as average response time cannot be expressed with weighted automata. In this work, we introduce nested weighted automata as a new formalism for expressing important quantitative properties such as average response time. We establish an almost complete decidability picture for the basic decision problems for nested weighted automata, and illustrate its applicability in several domains. },
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
issn = {2664-1690},
pages = {27},
publisher = {IST Austria},
title = {{Nested weighted automata}},
doi = {10.15479/AT:IST-2014-170-v1-1},
year = {2014},
}
@misc{5416,
abstract = {As hybrid systems involve continuous behaviors, they should be evaluated by quantitative methods, rather than qualitative methods. In this paper we adapt a quantitative framework, called model measuring, to the hybrid systems domain. The model-measuring problem asks, given a model M and a specification, what is the maximal distance such that all models within that distance from M satisfy (or violate) the specification. A distance function on models is given as part of the input of the problem. Distances, especially related to continuous behaviors are more natural in the hybrid case than the discrete case. We are interested in distances represented by monotonic hybrid automata, a hybrid counterpart of (discrete) weighted automata, whose recognized timed languages are monotone (w.r.t. inclusion) in the values of parameters.The contributions of this paper are twofold. First, we give sufficient conditions under which the model-measuring problem can be solved. Second, we discuss the modeling of distances and applications of the model-measuring problem.},
author = {Henzinger, Thomas A and Otop, Jan},
issn = {2664-1690},
pages = {22},
publisher = {IST Austria},
title = {{Model measuring for hybrid systems}},
doi = {10.15479/AT:IST-2014-171-v1-1},
year = {2014},
}
@misc{5417,
abstract = {We define the model-measuring problem: given a model M and specification φ, what is the maximal distance ρ such that all models M'within distance ρ from M satisfy (or violate)φ. The model measuring problem presupposes a distance function on models. We concentrate on automatic distance functions, which are defined by weighted automata.
The model-measuring problem subsumes several generalizations of the classical model-checking problem, in particular, quantitative model-checking problems that measure the degree of satisfaction of a specification, and robustness problems that measure how much a model can be perturbed without violating the specification.
We show that for automatic distance functions, and ω-regular linear-time and branching-time specifications, the model-measuring problem can be solved.
We use automata-theoretic model-checking methods for model measuring, replacing the emptiness question for standard word and tree automata by the optimal-weight question for the weighted versions of these automata. We consider weighted automata that accumulate weights by maximizing, summing, discounting, and limit averaging.
We give several examples of using the model-measuring problem to compute various notions of robustness and quantitative satisfaction for temporal specifications.},
author = {Henzinger, Thomas A and Otop, Jan},
issn = {2664-1690},
pages = {14},
publisher = {IST Austria},
title = {{From model checking to model measuring}},
doi = {10.15479/AT:IST-2014-172-v1-1},
year = {2014},
}
@misc{5428,
abstract = {Simulation is an attractive alternative for language inclusion for automata as it is an under-approximation of language inclusion, but usually has much lower complexity. For non-deterministic automata, while language inclusion is PSPACE-complete, simulation can be computed in polynomial time. Simulation has also been extended in two orthogonal directions, namely, (1) fair simulation, for simulation over specified set of infinite runs; and (2) quantitative simulation, for simulation between weighted automata. Again, while fair trace inclusion is PSPACE-complete, fair simulation can be computed in polynomial time. For weighted automata, the (quantitative) language inclusion problem is undecidable for mean-payoff automata and the decidability is open for discounted-sum automata, whereas the (quantitative) simulation reduce to mean-payoff games and discounted-sum games, which admit pseudo-polynomial time algorithms.
In this work, we study (quantitative) simulation for weighted automata with Büchi acceptance conditions, i.e., we generalize fair simulation from non-weighted automata to weighted automata. We show that imposing Büchi acceptance conditions on weighted automata changes many fundamental properties of the simulation games. For example, whereas for mean-payoff and discounted-sum games, the players do not need memory to play optimally; we show in contrast that for simulation games with Büchi acceptance conditions, (i) for mean-payoff objectives, optimal strategies for both players require infinite memory in general, and (ii) for discounted-sum objectives, optimal strategies need not exist for both players. While the simulation games with Büchi acceptance conditions are more complicated (e.g., due to infinite-memory requirements for mean-payoff objectives) as compared to their counterpart without Büchi acceptance conditions, we still present pseudo-polynomial time algorithms to solve simulation games with Büchi acceptance conditions for both weighted mean-payoff and weighted discounted-sum automata.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan and Velner, Yaron},
issn = {2664-1690},
pages = {26},
publisher = {IST Austria},
title = {{Quantitative fair simulation games}},
doi = {10.15479/AT:IST-2014-315-v1-1},
year = {2014},
}
@inproceedings{1392,
abstract = {Fault-tolerant distributed algorithms play an important role in ensuring the reliability of many software applications. In this paper we consider distributed algorithms whose computations are organized in rounds. To verify the correctness of such algorithms, we reason about (i) properties (such as invariants) of the state, (ii) the transitions controlled by the algorithm, and (iii) the communication graph. We introduce a logic that addresses these points, and contains set comprehensions with cardinality constraints, function symbols to describe the local states of each process, and a limited form of quantifier alternation to express the verification conditions. We show its use in automating the verification of consensus algorithms. In particular, we give a semi-decision procedure for the unsatisfiability problem of the logic and identify a decidable fragment. We successfully applied our framework to verify the correctness of a variety of consensus algorithms tolerant to both benign faults (message loss, process crashes) and value faults (message corruption).},
author = {Dragoi, Cezara and Henzinger, Thomas A and Veith, Helmut and Widder, Josef and Zufferey, Damien},
location = {San Diego, USA},
pages = {161 -- 181},
publisher = {Springer},
title = {{A logic-based framework for verifying consensus algorithms}},
doi = {10.1007/978-3-642-54013-4_10},
volume = {8318},
year = {2014},
}
@inproceedings{1393,
abstract = {Probabilistic programs are usual functional or imperative programs with two added constructs: (1) the ability to draw values at random from distributions, and (2) the ability to condition values of variables in a program via observations. Models from diverse application areas such as computer vision, coding theory, cryptographic protocols, biology and reliability analysis can be written as probabilistic programs. Probabilistic inference is the problem of computing an explicit representation of the probability distribution implicitly specified by a probabilistic program. Depending on the application, the desired output from inference may vary-we may want to estimate the expected value of some function f with respect to the distribution, or the mode of the distribution, or simply a set of samples drawn from the distribution. In this paper, we describe connections this research area called \Probabilistic Programming" has with programming languages and software engineering, and this includes language design, and the static and dynamic analysis of programs. We survey current state of the art and speculate on promising directions for future research.},
author = {Gordon, Andrew and Henzinger, Thomas A and Nori, Aditya and Rajamani, Sriram},
booktitle = {Proceedings of the on Future of Software Engineering},
location = {Hyderabad, India},
pages = {167 -- 181},
publisher = {ACM},
title = {{Probabilistic programming}},
doi = {10.1145/2593882.2593900},
year = {2014},
}
@inproceedings{2218,
abstract = {While fixing concurrency bugs, program repair algorithms may introduce new concurrency bugs. We present an algorithm that avoids such regressions. The solution space is given by a set of program transformations we consider in the repair process. These include reordering of instructions within a thread and inserting atomic sections. The new algorithm learns a constraint on the space of candidate solutions, from both positive examples (error-free traces) and counterexamples (error traces). From each counterexample, the algorithm learns a constraint necessary to remove the errors. From each positive examples, it learns a constraint that is necessary in order to prevent the repair from turning the trace into an error trace. We implemented the algorithm and evaluated it on simplified Linux device drivers with known bugs.},
author = {Cerny, Pavol and Henzinger, Thomas A and Radhakrishna, Arjun and Ryzhyk, Leonid and Tarrach, Thorsten},
isbn = {978-331908866-2},
location = {Vienna, Austria},
pages = {568 -- 584},
publisher = {Springer},
title = {{Regression-free synthesis for concurrency}},
doi = {10.1007/978-3-319-08867-9_38},
volume = {8559},
year = {2014},
}
@proceedings{2288,
abstract = {This book constitutes the proceedings of the 11th International Conference on Computational Methods in Systems Biology, CMSB 2013, held in Klosterneuburg, Austria, in September 2013. The 15 regular papers included in this volume were carefully reviewed and selected from 27 submissions. They deal with computational models for all levels, from molecular and cellular, to organs and entire organisms.},
editor = {Gupta, Ashutosh and Henzinger, Thomas A},
isbn = {978-3-642-40707-9},
location = {Klosterneuburg, Austria},
publisher = {Springer},
title = {{Computational Methods in Systems Biology}},
doi = {10.1007/978-3-642-40708-6},
volume = {8130},
year = {2013},
}
@article{2289,
abstract = {Formal verification aims to improve the quality of software by detecting errors before they do harm. At the basis of formal verification is the logical notion of correctness, which purports to capture whether or not a program behaves as desired. We suggest that the boolean partition of software into correct and incorrect programs falls short of the practical need to assess the behavior of software in a more nuanced fashion against multiple criteria. We therefore propose to introduce quantitative fitness measures for programs, specifically for measuring the function, performance, and robustness of reactive programs such as concurrent processes. This article describes the goals of the ERC Advanced Investigator Project QUAREM. The project aims to build and evaluate a theory of quantitative fitness measures for reactive models. Such a theory must strive to obtain quantitative generalizations of the paradigms that have been success stories in qualitative reactive modeling, such as compositionality, property-preserving abstraction and abstraction refinement, model checking, and synthesis. The theory will be evaluated not only in the context of software and hardware engineering, but also in the context of systems biology. In particular, we will use the quantitative reactive models and fitness measures developed in this project for testing hypotheses about the mechanisms behind data from biological experiments.},
author = {Henzinger, Thomas A},
journal = {Computer Science Research and Development},
number = {4},
pages = {331 -- 344},
publisher = {Springer},
title = {{Quantitative reactive modeling and verification}},
doi = {10.1007/s00450-013-0251-7},
volume = {28},
year = {2013},
}
@inproceedings{2298,
abstract = {We present a shape analysis for programs that manipulate overlaid data structures which share sets of objects. The abstract domain contains Separation Logic formulas that (1) combine a per-object separating conjunction with a per-field separating conjunction and (2) constrain a set of variables interpreted as sets of objects. The definition of the abstract domain operators is based on a notion of homomorphism between formulas, viewed as graphs, used recently to define optimal decision procedures for fragments of the Separation Logic. Based on a Frame Rule that supports the two versions of the separating conjunction, the analysis is able to reason in a modular manner about non-overlaid data structures and then, compose information only at a few program points, e.g., procedure returns. We have implemented this analysis in a prototype tool and applied it on several interesting case studies that manipulate overlaid and nested linked lists.
},
author = {Dragoi, Cezara and Enea, Constantin and Sighireanu, Mihaela},
location = {Seattle, WA, United States},
pages = {150 -- 171},
publisher = {Springer},
title = {{Local shape analysis for overlaid data structures}},
doi = {10.1007/978-3-642-38856-9_10},
volume = {7935},
year = {2013},
}
@article{2299,
abstract = {The standard hardware design flow involves: (a) design of an integrated circuit using a hardware description language, (b) extensive functional and formal verification, and (c) logical synthesis. However, the above-mentioned processes consume significant effort and time. An alternative approach is to use a formal specification language as a high-level hardware description language and synthesize hardware from formal specifications. Our work is a case study of the synthesis of the widely and industrially used AMBA AHB protocol from formal specifications. Bloem et al. presented the first formal specifications for the AMBA AHB Arbiter and synthesized the AHB Arbiter circuit. However, in the first formal specification some important assumptions were missing. Our contributions are as follows: (a) We present detailed formal specifications for the AHB Arbiter incorporating the missing details, and obtain significant improvements in the synthesis results (both with respect to the number of gates in the synthesized circuit and with respect to the time taken to synthesize the circuit), and (b) we present formal specifications to generate compact circuits for the remaining two main components of AMBA AHB, namely, AHB Master and AHB Slave. Thus with systematic description we are able to automatically and completely synthesize an important and widely used industrial protocol.},
author = {Godhal, Yashdeep and Chatterjee, Krishnendu and Henzinger, Thomas A},
journal = {International Journal on Software Tools for Technology Transfer},
number = {5-6},
pages = {585 -- 601},
publisher = {Springer},
title = {{Synthesis of AMBA AHB from formal specification: A case study}},
doi = {10.1007/s10009-011-0207-9},
volume = {15},
year = {2013},
}
@inproceedings{2301,
abstract = {We describe the design and implementation of P, a domain-specific language to write asynchronous event driven code. P allows the programmer to specify the system as a collection of interacting state machines, which communicate with each other using events. P unifies modeling and programming into one activity for the programmer. Not only can a P program be compiled into executable code, but it can also be tested using model checking techniques. P allows the programmer to specify the environment, used to "close" the system during testing, as nondeterministic ghost machines. Ghost machines are erased during compilation to executable code; a type system ensures that the erasure is semantics preserving. The P language is designed so that a P program can be checked for responsiveness-the ability to handle every event in a timely manner. By default, a machine needs to handle every event that arrives in every state. But handling every event in every state is impractical. The language provides a notion of deferred events where the programmer can annotate when she wants to delay processing an event. The default safety checker looks for presence of unhan-dled events. The language also provides default liveness checks that an event cannot be potentially deferred forever. P was used to implement and verify the core of the USB device driver stack that ships with Microsoft Windows 8. The resulting driver is more reliable and performs better than its prior incarnation (which did not use P); we have more confidence in the robustness of its design due to the language abstractions and verification provided by P.},
author = {Desai, Ankush and Gupta, Vivek and Jackson, Ethan and Qadeer, Shaz and Rajamani, Sriram and Zufferey, Damien},
booktitle = {Proceedings of the 34th ACM SIGPLAN Conference on Programming Language Design and Implementation},
location = {Seattle, WA, United States},
pages = {321 -- 331},
publisher = {ACM},
title = {{P: Safe asynchronous event-driven programming}},
doi = {10.1145/2491956.2462184},
year = {2013},
}
@inproceedings{2327,
abstract = {We define the model-measuring problem: given a model M and specification φ, what is the maximal distance ρ such that all models M′ within distance ρ from M satisfy (or violate) φ. The model measuring problem presupposes a distance function on models. We concentrate on automatic distance functions, which are defined by weighted automata. The model-measuring problem subsumes several generalizations of the classical model-checking problem, in particular, quantitative model-checking problems that measure the degree of satisfaction of a specification, and robustness problems that measure how much a model can be perturbed without violating the specification. We show that for automatic distance functions, and ω-regular linear-time and branching-time specifications, the model-measuring problem can be solved. We use automata-theoretic model-checking methods for model measuring, replacing the emptiness question for standard word and tree automata by the optimal-weight question for the weighted versions of these automata. We consider weighted automata that accumulate weights by maximizing, summing, discounting, and limit averaging. We give several examples of using the model-measuring problem to compute various notions of robustness and quantitative satisfaction for temporal specifications.},
author = {Henzinger, Thomas A and Otop, Jan},
location = {Buenos Aires, Argentina},
pages = {273 -- 287},
publisher = {Springer},
title = {{From model checking to model measuring}},
doi = {10.1007/978-3-642-40184-8_20},
volume = {8052},
year = {2013},
}
@inproceedings{2328,
abstract = {Linearizability of concurrent data structures is usually proved by monolithic simulation arguments relying on identifying the so-called linearization points. Regrettably, such proofs, whether manual or automatic, are often complicated and scale poorly to advanced non-blocking concurrency patterns, such as helping and optimistic updates.
In response, we propose a more modular way of checking linearizability of concurrent queue algorithms that does not involve identifying linearization points. We reduce the task of proving linearizability with respect to the queue specification to establishing four basic properties, each of which can be proved independently by simpler arguments. As a demonstration of our approach, we verify the Herlihy and Wing queue, an algorithm that is challenging to verify by a simulation proof.},
author = {Henzinger, Thomas A and Sezgin, Ali and Vafeiadis, Viktor},
location = {Buenos Aires, Argentina},
pages = {242 -- 256},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Aspect-oriented linearizability proofs}},
doi = {10.1007/978-3-642-40184-8_18},
volume = {8052},
year = {2013},
}
@inproceedings{2447,
abstract = {Separation logic (SL) has gained widespread popularity because of its ability to succinctly express complex invariants of a program’s heap configurations. Several specialized provers have been developed for decidable SL fragments. However, these provers cannot be easily extended or combined with solvers for other theories that are important in program verification, e.g., linear arithmetic. In this paper, we present a reduction of decidable SL fragments to a decidable first-order theory that fits well into the satisfiability modulo theories (SMT) framework. We show how to use this reduction to automate satisfiability, entailment, frame inference, and abduction problems for separation logic using SMT solvers. Our approach provides a simple method of integrating separation logic into existing verification tools that provide SMT backends, and an elegant way of combining SL fragments with other decidable first-order theories. We implemented this approach in a verification tool and applied it to heap-manipulating programs whose verification involves reasoning in theory combinations.
},
author = {Piskac, Ruzica and Wies, Thomas and Zufferey, Damien},
location = {St. Petersburg, Russia},
pages = {773 -- 789},
publisher = {Springer},
title = {{Automating separation logic using SMT}},
doi = {10.1007/978-3-642-39799-8_54},
volume = {8044},
year = {2013},
}
@inproceedings{2517,
abstract = {Traditional formal methods are based on a Boolean satisfaction notion: a reactive system satisfies, or not, a given specification. We generalize formal methods to also address the quality of systems. As an adequate specification formalism we introduce the linear temporal logic LTL[F]. The satisfaction value of an LTL[F] formula is a number between 0 and 1, describing the quality of the satisfaction. The logic generalizes traditional LTL by augmenting it with a (parameterized) set F of arbitrary functions over the interval [0,1]. For example, F may contain the maximum or minimum between the satisfaction values of subformulas, their product, and their average. The classical decision problems in formal methods, such as satisfiability, model checking, and synthesis, are generalized to search and optimization problems in the quantitative setting. For example, model checking asks for the quality in which a specification is satisfied, and synthesis returns a system satisfying the specification with the highest quality. Reasoning about quality gives rise to other natural questions, like the distance between specifications. We formalize these basic questions and study them for LTL[F]. By extending the automata-theoretic approach for LTL to a setting that takes quality into an account, we are able to solve the above problems and show that reasoning about LTL[F] has roughly the same complexity as reasoning about traditional LTL.},
author = {Almagor, Shaull and Boker, Udi and Kupferman, Orna},
location = {Riga, Latvia},
number = {Part 2},
pages = {15 -- 27},
publisher = {Springer},
title = {{Formalizing and reasoning about quality}},
doi = {10.1007/978-3-642-39212-2_3},
volume = {7966},
year = {2013},
}