Group protocol for distributed replicated objects

In group protocols, larger computation and communication are consumed to causally order all messages transmitted in the network. Transactions in clients manipulate objects in servers by sending read and write requests to the servers. In this paper we define significant messages, which are to be ordered at the application level, by using a conflicting relation among the transactions. We newly propose an object vector to causally order only the significant messages. The scheme of the object vector is invariant in the change of the group membership. We also show a TBCO (transaction-based causally ordered) protocol adopting the object vector; by which the number of messages to be causally ordered are reduced.