Figure 1(B) shows the state transition diagram for an optimistic replication model. The optimistic replication diagram differs from the pessimistic diagram (Figure 1(A)) in two ways: First, it has an extra state for conflict resolution. The component transitions to the Conflict state when the replica detects the primary replica version and the client replica version are concurrent (i.e., it is not possible to determine a partial ordering for the two versions) [15]. The component transitions back to the Dirty state once the client replica reads the conflicting version and resolves the conflict. Second, transitions from the Clean and Partial-Clean states to the Empty state occur when the client replica learns that the primary replica has a more recent version for the component. The decision of when to transition to Empty is left to the implementation. Some implementations may eagerly invalidate the current version, while others may allow the user to keep working with the current version. In other words, it is the implementation's responsibility to decide how eagerly it wants to act on the consistency information it receives.