Introduction to the
Sequence Diagram, also known as Sequence Diagram, Sequence Diagram or Sequence Diagram, is a KIND of UML interaction Diagram.
It shows dynamic collaboration between multiple objects by describing the chronological order in which messages are sent between them.
Can show interaction order, chronological order, concurrent process
The sequence diagram is divided into two directions: horizontal (objects) and vertical (time axis). The solid and dotted arrows in the middle represent between objectsPass the message to call the method.
Messages are passed horizontally between objects, arranged vertically in chronological order
The six elements of the sequence diagram
Roles: people, systems, subsystems, etc
Objects: Objects represent the roles that objects in the sequence diagram play in the interaction
Lifeline (timeline) : Represents the life time of the object
Control focus/activation: a symbol for a period of time, represented by a small rectangle, during which an object is activated to perform an action
Messages can be divided into synchronous messages, asynchronous messages, return messages, and self-associated messages
Self-associated message: This object invokes its own methods
fragment
Fragments should be used to distinguish between conditions required to invoke a method, not to determine events after a method is invoked
Alt (judge)
Loop (loop)
Opt (switch)
Par (parallel)
Dashed line: the lifetime of the object
