Concurrency control and view notification algorithms for collaborative replicated objects

Abstract

This paper describes algorithms for implementing a high-level programming model for synchronous distributed groupware applications. In this model, several application data objects may be atomically updated, and these objects automatically maintain consistency with their replicas using an optimistic algorithm. Changes to these objects may be optimistically or pessimistically observed by view objects by taking consistent snapshots. The algorithms for both update propagation and view notification are based upon optimistic guess propagation principles, adapted for fast commit by using primary copy replication techniques. The main contribution of the paper is the synthesis of these two algorithmic techniques - guess propagation and primary copy replication - for implementing a framework that is easy to program to and is well suited for the needs of groupware applications.