The logical clock timestamp scheme presented in this chapter provides the following guarantee: If event A happens before event B, then the timestamp of A is less than the timestamp of B. Note, however, that one cannot order two events based only on their timestamps. The fact that an event C has a timestamp that is less than the timestamp of event D does not necessarily mean that event C happened before event D; C and D could be concurrent events in the system. Discuss ways in which the logical clock timestamp scheme could be extended to distinguish concurrent events from events that can be ordered by the happens-before relationship.