TY - JOUR
AB - Giotto provides an abstract programmer's model for the implementation of embedded control systems with hard real-time constraints. A typical control application consists of periodic software tasks together with a mode-switching logic for enabling and disabling tasks. Giotto specifies time-triggered sensor readings, task invocations, actuator updates, and mode switches independent of any implementation platform. Giotto can be annotated with platform constraints such as task-to-host mappings, and task and communication schedules. The annotations are directives for the Giotto compiler, but they do not alter the functionality and timing of a Giotto program. By separating the platform-independent from the platform-dependent concerns, Giotto enables a great deal of flexibility in choosing control platforms as well as a great deal of automation in the validation and synthesis of control software. The time-triggered nature of Giotto achieves timing predictability, which makes Giotto particularly suitable for safety-critical applications.
AU - Thomas Henzinger
AU - Horowitz, Benjamin
AU - Kirsch, Christoph M
ID - 4469
IS - 1
JF - Proceedings of the IEEE
TI - Giotto: A time-triggered language for embedded programming
VL - 91
ER -
TY - CONF
AB - We present a formalism for specifying component interfaces that expose component requirements on limited resources. The formalism permits an algorithmic check if two or more components, when put together, exceed the available resources. Moreover, the formalism can be used to compute the quantity of resources necessary for satisfying the requirements of a collection of components. The formalism can be instantiated in several ways. For example, several components may draw power from the same source. Then, the formalism supports compatibility checks such as: can two components, when put together, achieve their tasks without ever exceeding the available amount of peak power? or, can they achieve their tasks by using no more than the initially available amount of energy (i.e., power accumulated over time)? The corresponding quantitative questions that our algorithms answer are the following: what is the amount of peak power needed for two components to be put together? what is the corresponding amount of initial energy? To solve these questions, we model interfaces with resource requirements as games with quantitative objectives. The games are played on state spaces where each state is labeled by a number (representing, e.g., power consumption), and a play produces an infinite path of labels. The objective may be, for example, to minimize the largest label that occurs during a play. We illustrate our approach by modeling compatibility questions for the components of robot control software, and of wireless sensor networks.
AU - Chakrabarti, Arindam
AU - de Alfaro, Luca
AU - Thomas Henzinger
AU - Stoelinga, Mariëlle
ID - 4561
TI - Resource interfaces
VL - 2855
ER -
TY - CONF
AB - Discounting the future means that the value, today, of a unit payoffis 1 if the payoffo ccurs today, a if it occurs tomorrow, a 2 if it occurs the day after tomorrow, and so on, for some real-valued discount factor 0 < a < 1. Discounting (or inflation) is a key paradigm in economics and has been studied in Markov decision processes as well as game theory. We submit that discounting also has a natural place in systems engineering: for nonterminating systems, a potential bug in the far-away future is less troubling than a potential bug today. We therefore develop a systems theory with discounting. Our theory includes several basic elements: discounted versions of system properties that correspond to the ω-regular properties, fixpoint-based algorithms for checking discounted properties, and a quantitative notion of bisimilarity for capturing the difference between two states with respect to discounted properties. We present the theory in a general form that applies to probabilistic systems as well as multicomponent systems (games), but it readily specializes to classical transition systems. We show that discounting, besides its natural practical appeal, has also several mathematical benefits. First, the resulting theory is robust, in that small perturbations of a system can cause only small changes in the properties of the system. Second, the theory is computational, in that the values of discounted properties, as well as the discounted bisimilarity distance between states, can be computed to any desired degree of precision.
AU - de Alfaro, Luca
AU - Thomas Henzinger
AU - Majumdar, Ritankar S
ID - 4628
TI - Discounting the future in systems theory
VL - 2719
ER -
TY - CONF
AB - We consider concurrent two-person games played in real time, in which the players decide both which action to play, and when to play it. Such timed games differ from untimed games in two essential ways. First, players can take each other by surprise, because actions are played with delays that cannot be anticipated by the opponent. Second, a player should not be able to win the game by preventing time from diverging. We present a model of timed games that preserves the element of surprise and accounts for time divergence in a way that treats both players symmetrically and applies to all ω-regular winning conditions. We prove that the ability to take each other by surprise adds extra power to the players. For the case that the games are specified in the style of timed automata, we provide symbolic algorithms for their solution with respect to all ω-regular winning conditions. We also show that for these timed games, memory strategies are more powerful than memoryless strategies already in the case of reachability objectives.
AU - de Alfaro, Luca
AU - Faella, Marco
AU - Thomas Henzinger
AU - Majumdar, Ritankar S
AU - Stoelinga, Mariëlle
ID - 4630
TI - The element of surprise in timed games
VL - 2761
ER -
TY - JOUR
AB - We study the free expansion of a pancake-shaped Bose-condensed gas, which is initially trapped under harmonic confinement and containing a vortex at its centre. In the case of a radial expansion holding the axial confinement fixed we consider various models for the interactions, depending on the thickness of the condensate relative to the value of the scattering length. We are thus able to evaluate different scattering regimes ranging from quasi-three-dimensional (Q3D) to strictly two-dimensional (2D). We find that as the system goes from Q3D to 2D the expansion rate of the condensate increases whereas that of the vortex core decreases. In the Q3D scattering regime we also examine a fully free expansion in 3D and find oscillatory behaviour for the vortex core radius: an initial fast expansion of the vortex core is followed by a slowing down. Such a nonuniform expansion rate of the vortex core implies that the timing of its observation should be chosen appropriately.
AU - Onur Hosten
AU - Vignolo, Patrizia
AU - Minguzzi, Anna
AU - Tanatar, Bilal
AU - Tosi, Mario P
ID - 576
IS - 12
JF - Journal of Physics B: Atomic, Molecular and Optical Physics
TI - Free expansion of two-dimensional condensates with a vortex
VL - 36
ER -