Steward: Scaling Byzantine Fault-Tolerant Replication to Wide Area Networks

This paper presents the first hierarchical Byzantine fault-tolerant replication architecture suitable to systems that span multiple wide-area sites. The architecture confines the effects of any malicious replica to its local site, reduces message complexity of wide-area communication, and allows read-only queries to be performed locally within a site for the price of additional standard hardware. We present proofs that our algorithm provides safety and liveness properties. A prototype implementation is evaluated over several network topologies and is compared with a flat Byzantine fault-tolerant approach. The experimental results show considerable improvement over flat Byzantine replication algorithms, bringing the performance of Byzantine replication closer to existing benign fault-tolerant replication techniques over wide area networks.     

Hierarchical edge bundles: visualization of adjacency relations in hierarchical data

A compound graph is a frequently encountered type of data set. Relations are given between items, and a hierarchy is defined on the items as well. We present a new method for visualizing such compound graphs. Our approach is based on visually bundling the adjacency edges, i.e., non-hierarchical edges, together. We realize this as follows. We assume that the hierarchy is shown via a standard tree visualization method. Next, we bend each adjacency edge, modeled as a B-spline curve, toward the polyline defined by the path via the inclusion edges from one node to another. This hierarchical bundling reduces visual clutter and also visualizes implicit adjacency edges between parent nodes that are the result of explicit adjacency edges between their respective child nodes. Furthermore, hierarchical edge bundling is a generic method which can be used in conjunction with existing tree visualization techniques. We illustrate our technique by providing example visualizations and discuss the results based on an informal evaluation provided by potential users of such visualizations     

Grigorii Valentinovich Samsonov

Obituaries

Grigorii Valentinovich Samsonov     

Parameterized Two-Player Nash Equilibrium

We study the problem of computing Nash equilibria in a two-player normal form (bimatrix) game from the perspective of parameterized complexity. Recent results proved hardness for a number of variants, when parameterized by the support size. We complement those results, by identifying three cases in which the problem becomes fixed-parameter tractable. Our results are based on a graph-theoretic representation of a bimatrix game, and on applying graph-theoretic tools on this representation.     

Maintaining Privacy on a Line

Consider a situation where people have to choose among a sequence of n linearly ordered positions to perform some task requiring a certain amount of privacy. Which position should one choose so as to maximize one’s privacy, i.e., minimize the chances that one of your neighboring positions becomes occupied by a later arrival? In this paper, we attempt to answer this question under a variety of models for the behavior of the later arrivals. Our results suggest that for the most part one should probably choose one of the extreme positions (with some interesting exceptions). We also suggest a number of variations on the problem that lead to many open problems.     

Integrated manufacturing,employee and business performance: Australian and New Zealand evidence

This article reports on a large field study of Integrated Manufacturing (IM), consisting of Total Quality Management (TQM), Just in Time (JIT) and Advanced Manufacturing Technology (AMT). The relationship between these facets of Integrated Manufacturing and performance was examined empirically, including measures of employee performance and manufacturing performance. There was a significant correlation between employee performance and manufacturing performance. While all three facets of Integrated Manufacturing were relatively strongly connected with employee performance, manufacturing performance was significantly but less strongly connected to the intensity of TQM and JIT than employee performance, and not connected with the intensity of Advanced Manufacturing Technology. Some second-order interactive effects between the facets of Integrated Manufacturing and performance were found. Further, by partitioning the large data set into three using the AMT factor as a cutting variable, it was found that the stronger the AMT environment, the stronger the explanatory power of TQM and JIT on both employee and manufacturing performance. The interactive impact of AMT and TQM was significantly positively related to both employee and manufacturing performance.