Usecase Diagram

Hello peeps !!

Long time no post because so many test and assignment .I wanna post about USE CASE DIAGRAM!!Well,ive no idea about this one ,I taking business electronic  I don’t like that !!As you can its still MESSY im a beginner :D but I tried do the best :P .

Here’s a little bit theory about usecase :

From Goals to Use Cases

Here’s a common scenario for many of us who have learned about uses cases but haven’t written one yet: You’ve identified the actors for your project. You’ve brainstormed a list of goals for each actor. You’re ready to create your first set of use cases. And you feel stuck. Or at least uncertain. Call it use case writer’s block. You could point to a use case if you saw one, but what are your use cases?

Use Case

A use case can be defined as [1] a functionality that a system can provide by interacting with the actor(s).

Continuing with the example of the ATM, withdraw cash is a functonality that the ATM provides. Therefore, this is a use case. Other possible use cases includes ,check balance, change PIN, and so on.

Use cases include both successful and unsuccessful scenarios of user interactions with the system. For example, authentication of a customer by the ATM would fail if he enters wrong PIN. In such case, an error message is displayed on the screen of the ATM.

Graphical Representation

An actor is represented by a stick figure and name of the actor is written below it. A use case is depicted by an ellipse and label of the use case is written inside it. The subject could be shown by drawing a rectangle. Label for the system could be put inside it either at the top or near the bottom. Use cases are enclosed inside the rectangle and actors are drawn outside the rectangle, as shown in figure - 01.

 

Association between Actors and Use Cases

A use case describes a specific functionality that the system provides to its users. The functionality is triggered by actor. Actors are connected to use cases through binary associations. The association indicates that the actor and use case communicates through message passing.

An actor must be associated with atleast one use case. Similarly, a given use case must be associated with atleast one actor. However, when a use case is associated with multiple actors, it might not be clear who triggers the functionality. No association among the actors are shown.

Use Case Relationships

Three types of relationships exist among use cases:

·          Include relationship

·         Extend relationship

·         Use case generalization

Include Relationship

Include relationships are used to depict similar behaviour that are shared by multiple use cases without replicating the common behaviour in each of those use cases.
Example

For example, consider an email application. A user can send a new mail, reply to an email he has received, or forward an email. However, in each of these three cases, the user must be logged in to perform those actions. Thus, we could have a login use case, which is included by compose mail, reply, and forward email use cases. The relationship is shown in figure - 02.