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Sequence Diagram - Coggle Diagram
Sequence Diagram
A. Key Elements
Object -system
Actor-outside the system
Lifelines
Messages
Activation Boxes
B. Notions and their significance
Object
Represented by boxes
Objects are placed in order they occur
Actor
Represented by a stick man
Actors are external objects so they do not have an activation box
Lifelines
Represented by a vertical dash line that shows the existence of the object and an actor over time
As they move down the lifeline it means that more time is passing
Messages
Shows the information being sent between objects
Moves down the lifelines with each message from Actor to Object
It is represented by a solid line with an arrow when the messages are moving from the requested to the receiver in and out is represented as a return message by a dashed line arrow moving in the opposite direction from the receiving object to the requesting object.
Messages are placed on the lines with the direction that they go in. Each message line from an actor or object moves down a few inches to represent information.
Messages moving in the opposite direction with a solid line arrow (from right to left) is not responding to information but requesting information / ending transaction
Alternative frame symbolizes a choice between two or more message sequences. Choices are usually mutually exclusive
It will be labelled as Alternative in the top left hand corner. There is a divider between the lines with a dash: one side labelled with the first outcome if action is correct and the second half as the else alternative
Represented by drawing boxes around the messages for the choices
Activation Boxes
shows when and how long an object is performing a process
Shows when objects are active and idle
A long rectangle box is drawn from the beginning of the object messages to the end of the last message. The one with the shortest rectangle length means the most idle
C. All other observations that makes the UML
Shows how objects in a system or classes in a code interact with each other
Shows interactions in a sequence order of how they occur
Used to document processes or understand the requirements of a new program
It is good to think of the parts of the system you are diagramming
They can get more complex