self-stabilizing

Consider a fully-connected synchronous distributed system consisting of n nodes, where up to f nodes may be faulty and every node starts in an arbitrary initial state. In the synchronous C-counting problem, all nodes need to eventually agree on a counter that is increased by one modulo C in each round for given C>1. In the self-stabilising firing squad problem, the task is to eventually guarantee that all non-faulty nodes have simultaneous responses to external inputs: if a subset of the correct nodes receive an external “go” signal as input, then all correct nodes should agree on a round (in the not-too-distant future) in which to jointly output a “fire” signal. Moreover, no node should generate a “fire” signal without some correct node having previously received a “go” signal as input. We present a framework reducing both tasks to binary consensus at very small cost. For example, we obtain a deterministic algorithm for self-stabilising Byzantine firing squads with optimal resilience f<n/3, asymptotically optimal stabilisation and response time O(f), and message size O(log f). As our framework does not restrict the type of consensus routines used, we also obtain efficient randomised solutions

Relating Knowledge and Coordinated Action: The Knowledge of Preconditions Principle

The Knowledge of Preconditions principle (KoP) is proposed as a widely applicable connection between knowledge and action in multi-agent systems. Roughly speaking, it asserts that if some condition is a necessary condition for performing a given action A, then knowing that this condition holds is also a necessary condition for performing A. Since the specifications of tasks often involve necessary conditions for actions, the KoP principle shows that such specifications induce knowledge preconditions for the actions. Distributed protocols or multi-agent plans that satisfy the specifications must ensure that this knowledge be attained, and that it is detected by the agents as a condition for action. The knowledge of preconditions principle is formalised in the runs and systems framework, and is proven to hold in a wide class of settings. Well-known connections between knowledge and coordinated action are extended and shown to derive directly from the KoP principle: a "common knowledge of preconditions" principle is established showing that common knowledge is a necessary condition for performing simultaneous actions, and a "nested knowledge of preconditions" principle is proven, showing that coordinating actions to be performed in linear temporal order requires a corresponding form of nested knowledge.Comment: In Proceedings TARK 2015, arXiv:1606.0729

Effects of attentional focus on kinematics and muscle activation patterns as a function of expertise

It has been demonstrated that for motor tasks, an external focus of attention can yield better results than an internal focus of attention. To be more specific, focusing on the effect of the movements seems to be more beneficial to performance and learning than focusing on the movements themselves (for a review, see Wulf & Prinz, 2001). To explain this phenomenon, Wulf, McNevin, and Shea (2001) proposed that an internal focus of attention is less effective because concentrating on the movements interferes with the motor system\u27s attempt to naturally self-organize, the constrained-action hypothesis. The purpose of this study was to find neurophysiological and/or mechanical evidence of this hypothesis using expert and novice American football field goal kickers (place kickers). Four experts and 12 novices (never kicked before) participated; they kicked seven kicks under control (no focus instructions), internal (focus on the part of the foot that would contact the ball), and external (focus on the part of the ball that would be contacted) focus conditions. (Abstract shortened by UMI.)

Volume 71 - Issue 8 - May, 1960

https://scholar.rose-hulman.edu/technic/1059/thumbnail.jp