Page 89 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Unit 7: Interaction Modelling

Notes
Figure 7.2: Components of Use Case Diagram

An actor represents a user or another system that will interact with the system you are modeling.

Did u know? A use case is an external view of the system that represents some action the
user might perform in order to complete a task.
Now we will discuss when to Use Cases Diagrams.
Use cases are used in almost every project. These are helpful in exposing requirements and
planning the project. During the initial stage of a project most use cases should be defined, but
as the project continues more might become visible.

Now let us see how to draw Use Cases Diagrams.
Use cases are a relatively easy UML diagram to draw, but this is a very simplified example. This
example is only meant as an introduction to the UML and use cases.

Start by listing a sequence of steps a user might take in order to complete an action.

Example: A user placing an order with a sales company might follow these steps.
1. Browse catalog and select items.
2. Call sales representative.
3. Supply shipping information.
4. Supply payment information.

5. Receive conformation number from salesperson.
These steps would generate this simple use case diagram.
Figure 7.3: Steps for Simple Use Case Diagram

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