Consistency in cooperative executions

Adluri, Vasantha Lakshmi (2002) Consistency in cooperative executions. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (13MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Computer-Supported Cooperative Work (CSCW) is the study of how computers can be used to help people work together. Cooperative work on shared, persistent data requires computing system support to coordinate the work of multiple users and to ensure data consistency. Attempts to extend the traditional concepts of transactions and serializability to specify consistency of cooperative executions have largely been unnatural and unsatisfactory. -- In this thesis, a new approach is presented to specify consistency of cooperative executions. It is based on an intuitive notion of legality of the read operations. Five legalities, each capturing a different notion of 'recentness' of the values, with respect to a defining relation are explored. They are stated formally in terms of system executions in shared read/write variables. A cooperative execution is consistent in a strong sense when all reads obey all legalities. By relaxing the legality requirements, and also by choosing different defining relations, a large variety of (weaker) consistencies can be specified in a hierarchical manner. -- We also give detailed algorithms for ensuring the various legalities. The algorithms correspond to three different environments - centralized, distributed, and mobile agent setups. We illustrate some examples where the legalities can be employed in various aspects of cooperative work.

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