Role use case diagram explanation
1. Definition and components of use case diagram
Use case diagrams are a requirement expression method often used when writing requirement descriptions. They are used to explain to development and testing colleagues the relationship between users and system functional units in the requirements.
It mainly consists of three parts: actors, use cases, and the relationship between actors and use cases.
Participant: It does not refer to people specifically, but refers to the role played by people outside the system in using the system or interacting with the system. Therefore, participants can be people, things, time or other systems, etc.
Use case: is a description of a sequence of actions, including variables, that the system performs and produces observable results that convey value to a specific actor.
Relationship: The relationship between actors and use cases mainly includes association, induction (generalization), inclusion, expansion and dependence.
2. Four types of relationships between participants and use cases
1. Relationship
Relationship description: represents the relationship between actors and use cases
Representation: A solid line with an arrow pointing to the use case.
Example: User logs into the system
2. Induction (generalization) relationship
Relationship description: Indicates the relationship between participants and between use cases and use cases. A use case can be specifically enumerated into one or more sub-use cases, which is called use case generalization.
Representation method: a solid line with a hollow arrow pointing to the generalized (inherited) use case, that is, the base use case/parent use case. (Note: The arrow of the generalization relationship does not point to being generalized, but to being inherited. Generalization and inheritance are different directions. Generalization is an abstract process from bottom to top, inheritance is from top to bottom, from general to Special process.)
For example: VIP members and ordinary users can be summarized as users; account login and WeChat login can also be summarized as login system.
3. Inclusion relationship
Relationship description: Indicates the relationship between use cases, in which the behavior of one use case (base use case) contains the behavior of another use case (containing use case).
Representation method: dotted arrow + the word <>, the arrow points to the included use case
For example: During the account login process, the user includes inputting the account number, entering the password, confirming the login, etc.
4. Expand relationships
Relationship description: Indicates the relationship between use cases; used to enhance the basic use case by extended use cases; extended use cases are use cases that will only be executed when specific conditions occur.
Representation method: dotted arrow + the word <>, the arrow points to the extended use case (i.e. basic use case)
Example: User forgets password during login process
3. Commonly used use case diagram software
There are many tools that can draw use case diagrams, such as traditional ones such as Word and PPT, and professional ones such as Visio and Edraw.
You can use visio to draw or draw online on the Internet
1. Confirm the elements of the use case diagram. What specific participants and use cases are there, and what is the relationship between participants and use cases;
2. Select the appropriate display symbol.
3. Connect actors and use cases according to determined relationships.
4. Label key elements with information.
In four simple steps, a use case diagram is completed.