The proposed distributed shared memory model is based on a data replication scheme that provides an environment for a collection of processes that interact to solve a parallel programming problem. In the implementation of the scheme the authors suppose that the replicas of the shared data are present at each node and that an appropriate coherence protocol for maintaining the consistency among the replicas is applied. The performance of the distributed computation is very sensitive to the data-access behavior of the application and to the applied coherence protocol. Communication cost is regarded as an appropriate performance measure. Therefore, the authors first introduce a model characterizing the computation behavior with five workload parameters. Second, they formally describe the coherence protocols as cooperating state machines in order to evaluate their communication costs as functions of workload parameters.< >