Describe in brief about the Sequence Diagrams

Sequence diagrams are interaction diagrams which emphasize time ordering of messages. In UML, it is shown as a table which shows objects arranged along the X axis and messages ordered in rising time along the Y axis. It has a global life line and focus of control. An object life line is vertical dashed line which represents existence of an object over a period of time. The focus of control is tall and thin rectangle which shows period during that an object is performing an action. The notation for depiction of sequence between objects with certain conditions is shown as:

                                                                              Figure: Sequence diagram