Only static behavior is not sufficient to model a system rather dynamic behavior is more important than static behavior. In UML, there are five diagrams available to model the dynamic nature and use case diagram is one of them. Now as we have to discuss that the use case diagram is dynamic in nature, there should be some internal or external factors for making the interaction.
These internal and external agents are known as actors. Use case diagrams consists of actors, use cases and their relationships. A single use case diagram captures a particular functionality of a system. The purpose of use case diagram is to capture the dynamic aspect of a system.
However, this definition is too generic to describe the purpose, as other four diagrams activity, sequence, collaboration, and Statechart also have the same purpose. We will look into some specific purpose, which will distinguish it from other four diagrams. Use case diagrams are used to gather the requirements of a system including internal and external influences.
These requirements are mostly design requirements. Hence, when a system is analyzed to gather its functionalities, use cases are prepared and actors are identified. Use case diagrams are considered for high level requirement analysis of a system.
When the requirements of a system are analyzed, the functionalities are captured in use cases. We can say that use cases are nothing but the system functionalities written in an organized manner. The second thing which is relevant to use cases are the actors. Actors can be defined as something that interacts with the system. Actors can be a human user, some internal applications, or may be some external applications. Variables, functional and all kinds of data etc, that is set as protected, can be accessed from parent to child use case.
For example, here anything can be inherited from place order use case to pay through pay and pay through credit card. Variables, functional and all kinds of data, etc that are set as protected, can be accessed from parent to child use case. For example, here anything can be inherited from authentication use case to authentication by fingerprints and authentication info. Suppose you need to make a software in which when the user confirms order and confirmation need the confirmation depends upon the product selection, calculation of price with tax and payment.
Payment can be through PayPal or credit card. Class diagrams and use case diagrams are used to illustrate systems based on the concept of UML Unified Modeling Language. For example, in the figure confirm the order is the base use case and payment is included use case.
It means that system will confirm the order if and only if the payment process will complete. You can click here to exercise the use case diagrams. By Prof. Fazal Rehman Shamil Last modified on April 7th, As you can see even a system as big as a vehicle sales system contains not more than 10 use cases! That's the beauty of use case modeling. The use case model also shows the use of extend and include. Besides, there are associations that connect between actors and use cases. Often, people find it easiest to start the requirements elicitation process by identifying the actors.
The following questions can help you identify the actors of your system Schneider and Winters - :. Identifying the Use Cases, and then the scenario-based elicitation process carries on by asking what externally visible, observable value that each actor desires. The following questions can be asked to identify use cases, once your actors have been identified Schneider and Winters - :. Use case granularity refers to the way in which information is organized within use case specifications, and to some extent, the level of detail at which they are written.
Achieving the right level of use case granularity eases communication between stakeholders and developers and improves project planning. Alastair Cockburn in Writing Effective Use Cases gives us an easy way to visualize different levels of goal level by thinking in terms of the sea:.
I hope you can answer "what is use case diagram" now and can apply use case in your project. It's time to draw a Use Case Diagram of your own. It's easy-to-use and intuitive. We use cookies to offer you a better experience. By visiting our website, you agree to the use of cookies as described in our Cookie Policy. What is Use Case Diagram?
A use case diagram is usually simple. It does not show the detail of the use cases: It only summarizes some of the relationships between use cases, actors, and systems. It does not show the order in which steps are performed to achieve the goals of each use case. You can describe those details in other UML diagram types and documents, and have them be linked from use cases. Use cases represent only the functional requirements of a system. Other requirements such as business rules, quality of service requirements, and implementation constraints must be represented separately, again, with other UML diagrams.
Free Download. Named by noun. Actor plays a role in the business Similar to the concept of user, but a user can play different roles For example: A prof. Actor has a responsibility toward the system inputs , and Actor has expectations from the system outputs.
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