I need the following after reviewing the paper Problem Statement – Issues discussed by the author Approach & design – How the authors approach to the issue &

Managing Update Conflicts in Bayou,

a Weakly Connected Replicated Storage System

Douglas B. Terry, Marvin M. Theimer, Karin Petersen, Alan J. Demers,

Mike J. Spreitzer and Carl H. Hauser

Computer Science Laboratory

Xerox Palo Alto Research Center

Palo Alto, California 94304 U.S.A.

Abstract

Bayou is a replicated, weakly consmtent storage system
designed for a mobile computing environment that includes porta-

ble machines with less than ideal network connectivity. To maxi-
mize availabdity, users can read and write any accessible replica.

Bayou’s design has focused on supporting apphcation-specific
mechanisms to detect and resolve the update conflicts that natu-

rally arise in such a system, ensuring that replicas move towards

eventual consistency, and defining a protocol by which the resolu-
tion of update conflicts stabilizes, It includes novel methods for
confhct detection, called dependency checks, and per-write con-
flict resolution based on client-provided merge procedures. To

guarantee eventual consistency, Bayou servers must be able to roll-
back the effects of previously executed writes and redo them
according to a global serialization order. Furthermore, Bayou per-

mits clients to observe the results of all writes received by a server,
mchrding tentative writes whose conflicts have not been ultimately
resolved. This paper presents the motivation for and design of
these mechanisms and describes the experiences gained with an

initial implementation of the system.

1. Introduction

The Bayou storage system prowdes an mfrastrtrcture for col-

laborative applications that manages the conflicts introduced by
concurrent activity while relying only on the weak connectivity
available for mobile computing. The advent of mobile computers,

in the form of laptops and personal digital assistants (PDAs)
enables the use of computational facilities away from the usual
work setting of users. However, mobile computers do not enjoy the

connectivity afforded by local area networks or the telephone sys-
tem. Even wireless media, such as cellular telephony, will not per-

mit continuous connectivity until per-mmute costs decline enough

to justify lengthy connections. Thus, the Bayou design requires

only occasional, patr-wise communication between computers.

This model takes into consideration characteristics of mobile com-

puting such as expensive connection time, frequent or occasional
disconnections, and that collaborating computers may never be all
connected simultaneously [1, 13, 16].

The Bayou architecture does not include the notion of a “dis-
connected” mode of operation because, in fact, various degrees of

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