Alan Fekete, M. Frans Kaashoek, and Nancy Lynch. Implementing Sequentially Consistent Shared Objects using Broadcast and Point-To-Point Communication. Proceedings of the 15th International Conference on Distributed Computing Systems, pages 439-449, Vancouver, Canada, May/June 1995, IEEE. .pdf

Abstract

A distributed algorithm that implements a sequentially consistent collection of shared read/update objects using a combination of broadcast and point-to-point communication is presented and proved correct. This algorithm is a generalization of one used in the Orca shared object system. The algorithm caches objects in the local memory of processors according to application needs; each read operation accesses a single copy of the object, while each update accesses all copies. Copies of all the objects are kept consistent using a strategy based on sequence numbers for broadcasts.

The algorithm is presented in two layers. The lower layer uses the given broadcast and point-to-point communication services, plus sequence numbers, to provide a new communication service called a {\em context multicast channel}. The higher layer uses a context multicast channel to manage the object replication in a consistent fashion. Both layers and their combination are described and verified formally, using the I/O automaton model for asynchronous concurrent systems.