Writing effective use cases

This tutorial will teach you how to use the actor grid and use case grid to create and manage actors and use cases. We will also teach writing flow of events with use case detail editor. Finally we will visualize use cases and actors with UML Use Case Diagram. Visual Paradigm for UML provides extensive modeling toolset for system analyst to write effective use case with use case diagram, flow of events editor and use case grid.

1. We first create actors using the Actors Grid. Select Tools > Model Element Grid > Open Actors Grid.
   
2. Click the Create Actor button at the top left hand corner to create new actor.
   
3. Name the actor as Order Process Clerk, the documentation of the actor can be specified directly in the Documentation pane.
   
4. Create two more actors, Customer Service Assistant and Inventory Control Clerk. Besides clicking the Create Actor button, you can press the Insert key to insert a new actor.
   

1. After creating actors, we now switch to create use cases. Select Tools > Model Element Grid > Open Use Cases Grid.
   
2. Similar to the Actors Grid, you can create use case with the Create Use Case button at the top left hand corner of the grid.
   
3. Name the use case as Place Order.
   
4. Let's create few more use cases, Check Order Status, Process Order, Schedule Delivery and Handle Goods Return.
   

1. We can define the details of a use case using the use case detail editor. Select the Place Order use case, and then click the Open Use Case Detail button.
   
2. We first switch to Info tab, and specify the Rank of the use case as High, and fill in the brief description in the Documentation field.
   
3. Switch to Flow of Events tab, and then specify the flow of events of the use case.
   
4. Switch to Details tab and specify more detail, such as Preconditions and Post-conditions for the use case.
   
5. Go back to Use Case Grid by clicking the Go to Grid button at the top right hand corner of Use Case Details editor.
   

1. After we define the details of the use case, we can now put it into diagram. Select the Place Order use case in the Use Case Grid, and press the Visualize button.
   
2. Let's visualize the Place Order use case in a new use case diagram. Select Create new diagram and leave the name as default in the Visualize Model Element dialog. Press the Create button to proceed.
   
3. Open Model Explorer, and drag the Customer Service Assistant actor to the newly created use case diagram.
   
4. Since the actor is not appearing on any diagram yet, you will be prompted to specify it as Master View in the project.
   
5. Connect the actor and use case by selecting the Association icon from actor, and drop it on the use case.
   
6. Open the use case detail again by right click on the use case, and select Use Case Details.
   
7. You can see the Customer Service Assistant now being specified in the Primary Actors field.
   
8. The supporting actors can be specified by pressing the + button next to Supporting Actors field, and select the actor from the list.
   
9. Let's create an extended use case from Place Order, name it as Process Out of Stock Order. Name the extension point as Out of Stock.
   
10. After that enter the documentation of the Process Out of Stock Order use case.
    

1. Switch back to the flow of events of Place Order use case. Let's add an extension for step 5 of the flow of events. Select step 5, then press the New Extension button.
   
2. The extended use case will be listed in the combo box in the Extension table. Let's select the Out of Stock use case.
   
3. The Out of Stock use case is now listed as the extension for step 5. Move your mouse cursor over it and the documentation of the Out of Stock use case will be shown.
   
4. You can jump to the Out of Stock use case or open its flow of events by right clicks on it.
   

Resources

1. sales_order_system.vpp