UML sequence diagram

See

http://blog.csdn.net/tianhai110/article/details/6361338


for a good summary, recommended.



Sequence diagrams are mainly used to show the sequence of interactions between objects.
Sequence diagrams represent interactions as a two-dimensional diagram. The vertical is the time axis, and time runs down the vertical line. The horizontal axis represents the taxonomic roles of individual objects in the collaboration. Class meta roles are represented by lifelines. When the object exists, the character is represented by a dashed line, and when the object's process is active, the lifeline is a two-way line.
Messages are represented by arrows from one object's lifeline to another object's lifeline. The arrows are arranged in chronological order from top to bottom in the figure.