What is the Difference Between Use Case Diagram and Activity Diagram?

Use case diagrams and activity diagrams are both Unified Modeling Language (UML) diagrams that describe the dynamic nature of a system, but they serve different purposes and have distinct features.

Use Case Diagram:

• Represents the user interactions within a system.
• Focuses on the system's functionality, i.e., what the system does, not how it is done.
• Shows the different ways a user may interact with a system.
• Has a low level of abstraction.

Activity Diagram:

• Models the workflow of the system.
• Represents the series of actions or flow control in a system.
• Shows how the system's workflow is implemented.
• Can be used to illustrate business processes or describe the steps of a use case.
• Has a higher level of abstraction compared to use case diagrams.

In summary, a use case diagram helps to model the system and user interactions, while an activity diagram helps to model the workflow of the system. An activity diagram shows the 'how' of a system, while a use case diagram shows the 'what'.

Comparative Table: Use Case Diagram vs Activity Diagram

Here is a table comparing the differences between Use Case Diagrams and Activity Diagrams:

In summary, a Use Case Diagram is designed to show the different ways a user may interact with a system, while an Activity Diagram models the workflow of the system, providing a detailed view of the sequence of actions or flow control in a system.