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Use Case Diagrams
Transcript of Use Case Diagrams
Use Case Diagram in Agile
Examples of Use Case Diagram
Wednesday, 14th December
Relationships within Use Case Diagram
shows what should happen in a system. They describe how the objects interact with each other to create a functioning system. Examples: Sequence Diagram/ Interaction Diagram/ Use Case Diagram
They enable the user to visualise different types of roles in a system and how those roles interact with the system
Depending on your requirement you can use that data in different ways. Below are few ways to use them.
• To identify functions and how roles interact with them – The primary purpose of use case diagrams.
• For a high level view of the system – Especially useful when presenting to managers or stakeholders. You can highlight the roles that interact with the system and the functionality provided by the system without going deep into inner workings of the system.
• To identify internal and external factors – This might sound simple but in large complex projects a system can be identified as an external role in another use case.
Use Case Diagrams
Actor in a use case diagram is any entity that performs a role in one given system. This could be a person, organization or an external system and usually drawn like skeleton shown below.
A use case represents a function or an action within the system. Its drawn as an oval and named with the function.
System is used to define the scope of the use case and drawn as a rectangle. This an optional element but useful when your visualizing large systems
A package object in a UML Class and Use Case Diagram provides the ability to group together classes and/or interfaces that are either similar in nature or related. Grouping these design elements in a package element provides for better readability of UML diagrams, especially complex diagrams.
There can be 4 relationship types in a use case diagram
between Actor and Use Case:
An actor must be associated with at least one use case.
An actor can be associated with multiple use cases.
Multiple actors can be associated with a single use case.
Generalization of an Actor
Generalization of an actor means that one actor can inherit the role of an other actor. The descendant inherits all the use cases of the ancestor. The descendant have one or more use cases that are specific to that role
Extend Relationship Between Two Use Cases
It extends the base use case and adds more functionality to the system.
show that the behavior of the included use case is part of the including (base) use case. The main reason for this is to reuse the common actions across multiple use cases. In some situations this is done to simplify complex behaviors. Few things to consider when using the <<include>> relationship.
Does not have to be perfect
Keep it as simple as possible
Record just enough information