Quorum-based replication in object-based systems

Objects are replicated in order to realize object-based systems. We discuss a novel quorum-based object locking (QOL) protocol which can be used to lock replicated objects by extending the traditional quorum-based protocols for simple read and write operations to abstract methods. If a pair of methods op(1) and op(2) are compatible, the summation of the quorum numbers of op(1) and op(2) can be smaller than the number of replicas in the QOL protocol even if op(1) or op(2) change the state of the object. We newly propose a version vector which can be used to identify which methods are performed on a replica. We discuss the QOL protocol, where the replicas exchange the compatible methods performed by themselves but not by others, by means of the version vector.