An Introduction to Use Case Diagrams: Features and Examples

Use case diagrams are a type of UML diagram that is commonly used to model the interactions between actors and a system in terms of the actions or use cases that they perform. These diagrams are useful in helping developers and stakeholders to understand the requirements of a system and how it should function. In this blog post, we’ll discuss the features of use case diagrams and provide some examples of how they can be used.

Features of Use Case Diagrams

Use case diagrams have several features that make them useful in modeling the functionality of a system. These features include:

1. Actors: Actors are external entities that interact with the system being modeled. Actors can be human users, other systems, or even hardware devices. Actors are depicted as stick figures in use case diagrams.
2. Use Cases: Use cases represent specific tasks or actions that the system can perform in response to user or external system requests. Use cases are depicted as ovals in use case diagrams.
3. Relationships: Use case diagrams use a variety of relationship types to show the interactions between actors and use cases. These relationships include “include” and “extend” relationships, which show how one use case can be included in another or how one use case can be extended by another.
4. System Boundary: The system boundary is a box that encloses all of the use cases and actors that are related to the system being modeled. This boundary helps to clarify the scope of the system and what is inside or outside of it.
5. Multiplicity: Multiplicity is used to indicate how many instances of each actor or use case are involved in a given interaction. It is usually represented using numbers or ranges.

Examples of Use Case Diagrams

To better understand how use case diagrams work, let’s look at some examples of how they can be used.

1.) Online Shopping System

One example of a use case diagram is an online shopping system. In this diagram, the actors are the customer and the system itself, while the use cases include “Browse Products,” “Add Item to Cart,” “Checkout,” and “Pay for Order.” The “Checkout” use case includes an “include” relationship with the “Add Item to Cart” use case, indicating that adding items to the cart is a necessary step in the checkout process.

2.) ATM System

Another example of a use case diagram is an ATM system. In this diagram, the actor is the customer and the use cases include “Withdraw Cash,” “Deposit Cash,” and “Check Account Balance.” The “Withdraw Cash” use case includes a “extend” relationship with the “Check Account Balance” use case, indicating that checking the account balance is an optional step that can be taken before withdrawing cash.

3.) Social Media System

A third example of a use case diagram is a social media system. In this diagram, the actors are the user and the system itself, while the use cases include “Create Profile,” “Post Content,” “View Content,” and “Comment on Content.” The “Post Content” use case includes an “extend” relationship with the “Create Profile” use case, indicating that creating a profile is a necessary step before being able to post content.

Conclusion

Use case diagrams are an important tool in modeling the functionality of a system. By clearly representing the interactions between actors and use cases, these diagrams can help developers and stakeholders to understand the requirements of the system and ensure that it functions as intended. Whether you’re modeling an online shopping system, an ATM system, or a social media platform, use case diagrams can provide a clear and concise visual representation of your system’s functionality.