Definition: it is a dynamic model diagram, which is used to show the relationship between objects, emphasize the message order between objects, and show the relationship between objects at the same time.

Elements include: object, activation, lifeline and message.

Function:

1, for business people, sequence diagrams can show how different business objects interact, which is very useful for communicating how the current business is going. In addition to recording the current events of the organization, the business-level sequence diagram can also be used as a requirement file to deliver the requirements of the future system.

2. For requirements analysts, sequence diagrams can take use cases to the next level by providing an in-depth expression. Usually use cases are refined into one or more sequence diagrams. One of the main purposes of sequence diagram is to transform the requirements expressed by use cases into further and deeper details.

3. For technicians, sequence diagrams are very useful for recording the behavior of future systems. In the design stage, architects and developers can use sequence diagrams to dig out the interaction between system objects and further improve the design of the whole system.