Group communication in partitionable systems: Specification and algorithms

We give a formal specification and an implementation for a partitionable group communication service in asynchronous distributed systems. Our specification is motivated by the requirements for building "partition-aware" applications that can continue operating without blocking in multiple concurrent partitions and reconfigure themselves dynamically when partitions merge. The specified service guarantees liveness and excludes trivial solutions, it constitutes a useful basis for building realistic partition-aware applications, and, it is implementable in practical asynchronous distributed systems where certain stability conditions hold.