Transaction-based causally ordered protocol for distributed replicated objects

In group communications, larger computation and communication overhead are considered to causally order all the 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 by using the 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 which adopts the object vector, by which the number of messages to be causally ordered are reduced.