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What is Use case?

What is Use Case

It is a text story/textual description that describe how user uses a system to accomplish a particular task. It is widely used to discover and record (mostly functional) requirement. It tells about some actor(s) using a system to meet specific goals. It answering questions like:

  • Who is using the system?
  • What are their typical scenarios of use?
  • What are their goals?
It is not object-oriented. It is not a diagram but UML use cases diagrams are “secondary-value” artifacts produced from use cases.

Example Use Case: Point of Sale
  1. The Customer arrives at a checkout (+goods).
  2. Cashier uses POS system to record items.
  3. The System presents a running total and line item details.
  4. The Customer enters payment information, which the system validates and records.
  5. System updates inventory.
  6. The Customer receives a receipt from the system and leaves.

Elements of Use Case
A Use Case can make with three things. They are Actors, Scenarios, and Use Cases.

  • Actor – An entity that shows a behavior, For example: a person (role), computer system, or organization
  • Scenario − specific sequence of actions and interactions between actors and a system. It is also called as use case instance. It is singe path of using the system. For example: the scenario of successfully purchasing 10 items with cash.
  • Use Case − It is a collection of related success and failure scenarios that describe an actor using a system to support a goal. For Example, a casual use case format with alternate scenarios:

Handle Returns

  • Main Success Scenario: A customer arrives at a checkout with items to return. The cashier uses the POS system to record each returned item …
  • Alternate Scenarios
    • If the customer paid by credit and the transaction to their credit account is rejected, inform the customer and pay them with cash.
    • If the item identifier is not found in the system. Notify the Cashier and suggest manual entry of the identifier code.
    • If the system detects failure to communicate with the external accounting system, …

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