Monotonic Prefix Consistency in Distributed Systems

We study the issue of data consistency in distributed systems. Specifically, we consider a distributed system that replicates its data at multiple sites, which is prone to partitions, and which is assumed to be available (in the sense that queries are always eventually answered). In such a setting, strong consistency, where all replicas of the system apply synchronously every operation, is not possible to implement. However, many weaker consistency criteria that allow a greater number of behaviors than strong consistency, are implementable in available distributed systems. We focus on determining the strongest consistency criterion that can be implemented in a convergent and available distributed system that tolerates partitions. We focus on objects where the set of operations can be split into updates and queries. We show that no criterion stronger than Monotonic Prefix Consistency (MPC) can be implemented.Comment: Submitted pape

Team Cognitive Ability as a Predictor of Team Performance

This manuscript presents two studies of the relationship between team cognitive ability (average Scholastic Aptitude Test score of team members) and team performance (a subjective coach\u27s evaluation and an objective measure using Sagarin\u27s Power Rankings) among NCAA Division 1 Men\u27s Basketball teams. Study 1 was conducted following the 1991-92 season whereas Study 2 was conducted during the 1993-94 season. Both studies indicated that team cognitive ability was significantly related to the coach\u27s evaluation but not to the power ranking measure, and that team strategy moderated the relationship between cognitive ability and the coach\u27s evaluation of performance. Cognitive ability moderated the relationship between team strategy and power ranking, but the nature of the interaction was different across the two studies

Concentration Characteristics and Batting Performance In Collegiate Baseball and Softball

This study examined relationships between batting performance, trait anxiety, and concentration style. A predictive analysis was also formed to determine the combination of subscales that may best explain variance in batting performance. To accurately measure these variables, the Sport Competition Anxiety Test (SCAT; Martens, Vealey, & Burton, 1990) and the Batting-specific Test of Attentional and Interpersonal Style (B-TAIS; Albrecht & Feltz, 1987) were employed. Participants consisted of both male collegiate baseball and female collegiate sofitball players located in the southeastern section of the United States. Participants\u27 2003 batting statistics were utilized to assess batting performance, and participants must have compiled at least 40 or more at-bats during the 2003 season to participate in the study. To calculate overall batting performance the OPS (on-base percentage plus slugging percentage) batting statistic was utilized. Results displayed no significant relationships between OPS and B-TAIS subscales among collegiate baseball participants. Also, no subscales explained variance in OPS. Significant relationships were found between collegiate softball, OPS, and B-TAISsubscales, and 17.3% (SE = .164) of the variance in OPS was explained by subscales INFP and RED. INFP was the best predictor of OPS (beta = .365). Sport competition anxiety was negatively associated with OPS for both baseball and softball participants. There were no significant correlational differences between OPS and B-TAIS subscales for gender

THE "POWER" OF TEXT PRODUCTION ACTIVITY IN COLLABORATIVE MODELING : NINE RECOMMENDATIONS TO MAKE A COMPUTER SUPPORTED SITUATION WORK

Language is not a direct translation of a speaker’s or writer’s knowledge or intentions. Various complex processes and strategies are involved in serving the needs of the audience: planning the message, describing some features of a model and not others, organizing an argument, adapting to the knowledge of the reader, meeting linguistic constraints, etc. As a consequence, when communicating about a model, or about knowledge, there is a complex interaction between knowledge and language. In this contribution, we address the question of the role of language in modeling, in the specific case of collaboration over a distance, via electronic exchange of written textual information. What are the problems/dimensions a language user has to deal with when communicating a (mental) model? What is the relationship between the nature of the knowledge to be communicated and linguistic production? What is the relationship between representations and produced text? In what sense can interactive learning systems serve as mediators or as obstacles to these processes

A Tour of Gallifrey, a Language for Geodistributed Programming

Programming efficient distributed, concurrent systems requires new abstractions that go beyond traditional sequential programming. But programmers already have trouble getting sequential code right, so simplicity is essential. The core problem is that low-latency, high-availability access to data requires replication of mutable state. Keeping replicas fully consistent is expensive, so the question is how to expose asynchronously replicated objects to programmers in a way that allows them to reason simply about their code. We propose an answer to this question in our ongoing work designing a new language, Gallifrey, which provides orthogonal replication through _restrictions_ with _merge strategies_, _contingencies_ for conflicts arising from concurrency, and _branches_, a novel concurrency control construct inspired by version control, to contain provisional behavior