A Sequence diagram is an interaction diagram that shows how
processes operate with one another and what is their order. It is
a construct of a Message Sequence Chart. A sequence diagram
shows object interactions arranged in time sequence.
It depicts the objects and classes involved in the scenario and
the sequence of messages exchanged between the objects
needed to carry out the functionality of the scenario. Sequence
diagrams are typically associated with use case realizations in
the Logical View of the system under development. Sequence
diagrams are sometimes called event diagrams or event
scenarios.