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Figure 2.6.
The external system actor Telecheck is incorporated into your use case model. |
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The noun opening deposit balance is a monetary amount. You might be tempted to model it as a class, but does it really exhibit behavior or have attributes? If it were a candidate class, it would have only one attribute (or property), and that would be Value. Identifying classes and members of classes (properties and methods) isn't always an easy process, and even the very best object technologists admit that sometimes they don't correctly identify classes the first time. On further analysis, you discover that opening deposit balance is actually a property of your Account class. How did you gather this? The adjective opening provides a big clue. It implies that something other than the object balance is going to fluctuate at some point in time. Balances fluctuate, but so do accounts. Then you remember that when you receive a monthly account statement from your bank, there is a beginning balance and an ending balance. Because the account statement is merely a snapshot (or instance) of your account information, you finally decide that Balance is an attribute of the Account class. In general, a good rule of thumb to use (loosely) is that if a candidate class has only one property (or attribute) and no methods, it can be a property of a larger class. |
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The verb phrase provides the customer information to the system (system now being Samsona Bank Teller System) indicates an action taken by the teller against the system. This action is also known as an event. You decide that this is a valid event, and, therefore, you incorporate this verb phrase into your sequence diagram. |
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The verb phrase check the customer's checking history is an action the teller carries out, using the interface to the Telecheck system. Therefore, you should incorporate it into your sequence diagram. |
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The verb phrase provides the opening deposit balance to the system (system now being Samsona Bank Teller System) specifies information about the new account, supplied by the teller. You should incorporate it into your sequence diagram. |
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