Developing distributed group communication in pSR

Persistent SR (pSR) is an extended version of the distributed and concurrent programming language SR (Synchronising Resources). Concurrency is extended through persistence in pSR because resources can exist independently of a particular program execution and thus act as shared objects. The paper describes a new extension to pSR, the introduction of groups and group communications, and how they interact with persistent resources. The novelty of this work is that it incorporates groups into a high level programming language. The groups extension raises three issues: how are groups to be expressed at the language level, what are the semantics of group communications, and how are they to be maintained efficiently at the system level? A prototype is built in pSR to enable testing and development. Group semantic options are described and implementation strategies for the maintenance of groups at the system level in a persistent distributed environment are investigated with reference to IP multicast.