1,721,033 research outputs found
Selecting a "Primary Partition" in Partitionable Asynchronous Distributed Systems
No full text{We consider network applications that are based on the process group paradigm. When such applications are deployed over networks that are subject to failures, they may partition across several disconnected clusters resulting in multiple views of the group's current composition to exist concurrently. Application semantics determine which operations, if any, can be performed in different partitions without compromising consistency. For certain application classes, most (possibly all) operations need to be confined to a single primary partition while other partitions are allowed to service only a (possibly empty) subset of the operations. In this paper, we propose a mechanism for deciding when a view constitutes the primary partition for the group. Our solution is highly flexible and has the following novel features: each group member can establish if it belongs to the primary partition or not based solely on local information; the group can be dynamic as processes voluntarily join and leave it; the selection rule for establishing the primary partition need not be universal but can be decided on a per-application basis and can be modified at run-time; the primary partition can be re-established even after total failures. Layering our solution on top of a partitionable group membership service allows a wide range of applications with different and possibly conflicting notions of "primary partition" to be supported on a common computing base.
Enriched view synchrony: a programming paradigm for partitionable asynchronous distributed systems
No full text
On programming with view synchrony
No full text{View synchrony has been proposed as a programming paradigm for developing reliable distributed applications. The paradigm is particularly attractive when the underlying computing system is asynchronous and prone to complex failure scenarios including partitions. View synchrony encourages a programming style where groups of processes cooperate closely in order to maintain some form of shared state among them. In this paper we examine the technical problems that arise in shared state management when programming applications using view synchrony. We identify three classes of problems corresponding to state transfer upon group joins, state recreation after total failures and state merging after partition unions. We argue that shared state problems are inherent to any implementation, and without explicit support, attempts to solve them may easily obscure much of the simplicity and elegance of view synchrony. Finally, we propose an extension to the traditional view synchrony model based on the notion of subviews that addresses the problems raised by shared state management
Group-Based Fault-Tolerance in Partitionable Asynchronous Distributed Systems
No full textWe consider the problem of developing reliable services to be deployed in partitionable asynchronous distributed systems. What makes this task difficult is guaranteeing the consistency of shared state despite failures and recoveries. While process groups and view-synchronous communication can significantly simplify reasoning about failures in such systems, they are insufficient for dealing with recoveries and merging of partitions after repairs. We define shared state reconciliation as the abstract characterization of recovery and show how view-synchronous communication can be enriched in order to solve it simply and systematically
Preface to special issue on cooperation in selfish systems
No full textThe problem of understanding the conditions under which cooperation or altruism can be sustained between interacting selfish entities is a fundamental issue in both biology and the social sciences
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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