Business Analyst: What is a use case diagram vs activity diagram?

Use case diagram — actors and functions. Activity diagram — process flow.

Use case diagram:

• High-level view.
• Shows actors.
• Shows system functions.
• No process details.

Activity diagram:

• Detailed flow.
• Shows steps.
• Shows decisions.
• Shows parallel activities.

When to use:

Key differences:

• Use case — what the system does.
• Activity — how it does it.