Master Defense, Michael G. Sørensen

Datalogisk Institut, N037 (stuen)
Monday, Januar 6th, 1997, 14.15 - 15.30

Pessimistic, Strict and Optimistic

A Mobility-Transparent Model for Consistency

Michael G. Sørensen

Master Student


The design, implementation, and evaluation of a mobility-transparent model for consistency is presented.

A distributed file system with support for mobile computing has been designed and implemented. The system enables applications to utilize any desired level of optimism or pessimism and to adapt their behaviour according to different communication characteristics or user demands. Guidelines for extending the system with a transactional facility are also given.

The distributed file system is based on a model that uses time as a consistency measure. Using such a scheme the applications can relax their consistency requirements as the quality of communication decreases in order to achieve higher availability or reduce cost, and strengthen them again when suited.

Keywords: mobile computing, distributed file systems, client/server, communication, adaptation, availability, consistency, file sharing semantics, replica control strategies, optimism, pessimism, caching, read and write operations, locks, conflict detection and resolution, transactions.

Konsulent: Birger Andersen
Censor: Arne Skou, IESD, Aalborg Universitet

PS: Efter forsvaret er der øl mm. i DistLab (N131).

Last modified: 18.04.2002 (Original version last modified: Fri Dec 20 16:00:54 MET, 1996)