TY - CONF
AB - The Hierarchical Timing Language (HTL) is a real-time coordination language for distributed control systems. HTL programs must be checked for well-formedness, race freedom, transmission safety (schedulability of inter-host communication), and time safety (schedulability of host computation). We present a modular abstract syntax and semantics for HTL, modular checks of well-formedness, race freedom, and transmission safety, and modular code distribution. Our contributions here complement previous results on HTL time safety and modular code generation. Modularity in HTL can be utilized in easy program composition as well as fast program analysis and code generation, but also in so-called runtime patching, where program components may be modified at runtime.
AU - Henzinger, Thomas A
AU - Kirsch, Christoph
AU - Marques, Eduardo
AU - Sokolova, Ana
ID - 3844
TI - Distributed, modular HTL
ER -
TY - JOUR
AB - Games on graphs with omega-regular objectives provide a model for the control and synthesis of reactive systems. Every omega-regular objective can be decomposed into a safety part and a liveness part. The liveness part ensures that something good happens “eventually.” Two main strengths of the classical, infinite-limit formulation of liveness are robustness (independence from the granularity of transitions) and simplicity (abstraction of complicated time bounds). However, the classical liveness formulation suffers from the drawback that the time until something good happens may be unbounded. A stronger formulation of liveness, so-called finitary liveness, overcomes this drawback, while still retaining robustness and simplicity. Finitary liveness requires that there exists an unknown, fixed bound b such that something good happens within b transitions. While for one-shot liveness (reachability) objectives, classical and finitary liveness coincide, for repeated liveness (Buchi) objectives, the finitary formulation is strictly stronger. In this work we study games with finitary parity and Streett objectives. We prove the determinacy of these games, present algorithms for solving these games, and characterize the memory requirements of winning strategies. We show that finitary parity games can be solved in polynomial time, which is not known for infinitary parity games. For finitary Streett games, we give an EXPTIME algorithm and show that the problem is NP-hard. Our algorithms can be used, for example, for synthesizing controllers that do not let the response time of a system increase without bound.
AU - Chatterjee, Krishnendu
AU - Henzinger, Thomas A
AU - Horn, Florian
ID - 3870
IS - 1
JF - ACM Transactions on Computational Logic (TOCL)
TI - Finitary winning in omega-regular games
VL - 11
ER -
TY - CONF
AB - Nondeterministic weighted automata are finite automata with numerical weights oil transitions. They define quantitative languages 1, that assign to each word v; a real number L(w). The value of ail infinite word w is computed as the maximal value of all runs over w, and the value of a run as the supremum, limsup liminf, limit average, or discounted sum of the transition weights. We introduce probabilistic weighted antomata, in which the transitions are chosen in a randomized (rather than nondeterministic) fashion. Under almost-sure semantics (resp. positive semantics), the value of a word v) is the largest real v such that the runs over w have value at least v with probability I (resp. positive probability). We study the classical questions of automata theory for probabilistic weighted automata: emptiness and universality, expressiveness, and closure under various operations oil languages. For quantitative languages, emptiness university axe defined as whether the value of some (resp. every) word exceeds a given threshold. We prove some, of these questions to he decidable, and others undecidable. Regarding expressive power, we show that probabilities allow its to define a wide variety of new classes of quantitative languages except for discounted-sum automata, where probabilistic choice is no more expressive than nondeterminism. Finally we live ail almost complete picture of the closure of various classes of probabilistic weighted automata for the following, provide, is operations oil quantitative languages: maximum, sum. and numerical complement.
AU - Chatterjee, Krishnendu
AU - Doyen, Laurent
AU - Henzinger, Thomas A
ID - 3871
TI - Probabilistic weighted automata
VL - 5710
ER -
TY - JOUR
AB - We compare anti-parasite defences at the level of multicellular organisms and insect societies, and find that selection by parasites at these two organisational levels is often very similar and has created a number of parallel evolutionary solutions in the host's immune response. The defence mechanisms of both individuals and insect colonies start with border defences to prevent parasite intake and are followed by soma defences that prevent the establishment and spread of the parasite between the body's cells or the social insect workers. Lastly, germ line defences are employed to inhibit infection of the reproductive tissue of organisms or the reproductive individuals in colonies. We further find sophisticated self/non-self-recognition systems operating at both levels, which appear to be vital in maintaining the integrity of the body or colony as a reproductive entity. We then expand on the regulation of immune responses and end with a contemplation of how evolution may shape the different immune components, both within and between levels. The aim of this review is to highlight common evolutionary principles acting in disease defence at the level of both individual organisms and societies, thereby linking the fields of physiological and ecological immunology.
AU - Cremer, Sylvia
AU - Sixt, Michael K
ID - 3946
IS - 1513
JF - Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
TI - Analogies in the evolution of individual and social immunity
VL - 364
ER -
TY - CONF
AB - We describe an algorithm for segmenting three-dimensional medical imaging data modeled as a continuous function on a 3-manifold. It is related to watershed algorithms developed in image processing but is closer to its mathematical roots, which are Morse theory and homological algebra. It allows for the implicit treatment of an underlying mesh, thus combining the structural integrity of its mathematical foundations with the computational efficiency of image processing.
AU - Edelsbrunner, Herbert
AU - Harer, John
ID - 3968
TI - The persistent Morse complex segmentation of a 3-manifold
VL - 5903
ER -
TY - JOUR
AB - Populations living in a spatially and temporally changing environment can adapt to the changing optimum and/or migrate toward favorable habitats. Here we extend previous analyses with a static optimum to allow the environment to vary in time as well as in space. The model follows both population dynamics and the trait mean under stabilizing selection, and the outcomes can be understood by comparing the loads due to genetic variance, dispersal, and temporal change. With fixed genetic variance, we obtain two regimes: (1) adaptation that is uniform along the environmental gradient and that responds to the moving optimum as expected for panmictic populations and when the spatial gradient is sufficiently steep, and (2) a population with limited range that adapts more slowly than the environmental optimum changes in both time and space; the population therefore becomes locally extinct and migrates toward suitable habitat. We also use a population‐genetic model with many loci to allow genetic variance to evolve, and we show that the only solution now has uniform adaptation.
AU - Polechova, Jitka
AU - Barton, Nicholas H
AU - Marion, Glenn
ID - 4136
IS - 5
JF - American Naturalist
TI - Species' range: Adaptation in space and time
VL - 174
ER -
TY - JOUR
AB - Felsenstein distinguished two ways by which selection can directly strengthen isolation. First, a modifier that strengthens prezygotic isolation can be favored everywhere. This fits with the traditional view of reinforcement as an adaptation to reduce deleterious hybridization by strengthening assortative mating. Second, selection can favor association between different incompatibilities, despite recombination. We generalize this “two allele” model to follow associations among any number of incompatibilities, which may include both assortment and hybrid inviability. Our key argument is that this process, of coupling between incompatibilities, may be quite different from the usual view of reinforcement: strong isolation can evolve through the coupling of any kind of incompatibility, whether prezygotic or postzygotic. Single locus incompatibilities become coupled because associations between them increase the variance in compatibility, which in turn increases mean fitness if there is positive epistasis. Multiple incompatibilities, each maintained by epistasis, can become coupled in the same way. In contrast, a single-locus incompatibility can become coupled with loci that reduce the viability of haploid hybrids because this reduces harmful recombination. We obtain simple approximations for the limits of tight linkage, and strong assortment, and show how assortment alleles can invade through associations with other components of reproductive isolation.
AU - Barton, Nicholas H
AU - De Cara, Maria
ID - 4242
IS - 5
JF - Evolution; International Journal of Organic Evolution
TI - The evolution of strong reproductive isolation
VL - 63
ER -
TY - CONF
AB - Pseudo-code descriptions of STMs assume sequentially consistent program execution and atomicity of high-level STM operations like read, write, and commit. These assumptions are often violated in realistic settings, as STM implementations run on relaxed memory models, with the atomicity of operations as provided by the hardware. This paper presents the first approach to verify STMs under relaxed memory models with atomicity of 32 bit loads and stores, and read-modify-write operations. We present RML, a new high-level language for expressing concurrent algorithms with a hardware-level atomicity of instructions, and whose semantics is parametrized by various relaxed memory models. We then present our tool, FOIL, which takes as input the RML description of an STM algorithm and the description of a memory model, and automatically determines the locations of fences, which if inserted, ensure the correctness of the STM algorithm under the given memory model. We use FOIL to verify DSTM, TL2, and McRT STM under the memory models of sequential consistency, total store order, partial store order, and relaxed memory order.
AU - Guerraoui, Rachid
AU - Thomas Henzinger
AU - Vasu Singh
ID - 4383
TI - Software transactional memory on relaxed memory models
VL - 5643
ER -
TY - CONF
AB - For programs whose data variables range over boolean or finite domains, program verification is decidable, and this forms the basis of recent tools for software model checking. In this paper, we consider algorithmic verification of programs that use boolean variables, and in addition, access a single read-only array whose length is potentially unbounded, and whose elements range over a potentially unbounded data domain. We show that the reachability problem, while undecidable in general, is (1) Pspace-complete for programs in which the array-accessing for-loops are not nested, (2) decidable for a restricted class of programs with doubly-nested loops. The second result establishes connections to automata and logics defining languages over data words.
AU - Alur, Rajeev
AU - Cerny, Pavol
AU - Weinstein, Scott
ID - 4403
TI - Algorithmic analysis of array-accessing programs
VL - 5771
ER -
TY - CONF
AB - We present an on-the-fly abstraction technique for infinite-state continuous -time Markov chains. We consider Markov chains that are specified by a finite set of transition classes. Such models naturally represent biochemical reactions and therefore play an important role in the stochastic modeling of biological systems. We approximate the transient probability distributions at various time instances by solving a sequence of dynamically constructed abstract models, each depending on the previous one. Each abstract model is a finite Markov chain that represents the behavior of the original, infinite chain during a specific time interval. Our approach provides complete information about probability distributions, not just about individual parameters like the mean. The error of each abstraction can be computed, and the precision of the abstraction refined when desired. We implemented the algorithm and demonstrate its usefulness and efficiency on several case studies from systems biology.
AU - Thomas Henzinger
AU - Maria Mateescu
AU - Wolf, Verena
ID - 4453
TI - Sliding-window abstraction for infinite Markov chains
VL - 5643
ER -