Question

Provide an example of a domain class, a design class, and an implementation class that might be used in the implementation of a bank ATM application. Explain why you chose each class.

Short answer

Domain Class: Account; Design Class: ATMTransaction; Implementation Class: BankDatabase.

Step-by-step solution

Define the Domain Class - Account

The domain class represents a real-world concept or entity in the domain of the application. For a bank ATM application, an example of a domain class could be `Account`. This class encapsulates the data and behavior related to a bank account, such as balance, account number, and operations like deposits and withdrawals. This choice reflects the core functionality and entities within the banking domain.

Define the Design Class - ATMTransaction

The design class takes part in the design phase and defines how the system integrates the domain concepts into software architecture. An example could be `ATMTransaction`, which manages the interaction between the account holder and the ATM machine. It can handle different types of transactions, like deposits, withdrawals, and checks. This choice is vital because it structures how domain classes interact within the system.

Define the Implementation Class - BankDatabase

The implementation class directly relates to coding the functionalities that were defined in the design class. The `BankDatabase` could be an implementation class, which handles data storage and retrieval related to all bank accounts. This includes functions to update account balances or retrieve account details based on transactions. This class is selected to manage how data is stored and accessed efficiently.

Key concepts

Domain Class - Account

The domain class is a cornerstone in software engineering, representing key entities within a specific domain. In the context of a bank ATM application, an "Account" is an ideal example of a domain class. This class is pivotal as it mirrors real-world concepts. Think of the things you can do with an account: checking the balance, making deposits, or withdrawing money. This class encapsulates these actions and the information that comes with them. Some essential characteristics of the "Account" domain class may include:

• Balance: The amount of money present.
• Account Number: A unique identifier for the account.
• Operations: Methods to handle deposits, withdrawals, etc.

By using the Account as a domain class, developers ensure the application accurately represents the financial relationships and processes users are accustomed to experiencing in real life. This class thus serves as the conceptual link between the software and the banking environment it simulates.

Design Class - ATMTransaction

Design classes play a critical role in the architecture of an application. They act as the bridge between domain classes and their implementation in the software system. In a bank ATM application, the "ATMTransaction" class is a fitting example. It orchestrates the interactions between the user and their account via the ATM. The purpose of this design class is to organize and define how transactions occur. It is not burdened with the specifics of storing data, but rather focuses on how these processes function. Key responsibilities of the "ATMTransaction" design class include:

• Transaction Types: Handling deposits, withdrawals, and balance inquiries.
• User Interface Interaction: Managing the exchange of commands and responses between the user and ATM.
• Transaction Sequencing: Ensuring logical and secure processing of different transactions.

The "ATMTransaction" class is vital for consistent integration of domain classes into a coherent software system, ensuring the ATM functions smoothly and logically from the user's point of view.

Implementation Class - BankDatabase

Implementation classes are the nuts and bolts of any software application—they deal with the actual data handling and processing functionalities. Within the ATM application, "BankDatabase" is a prime example of an implementation class. This class is responsible for the behind-the-scenes work. It effectively manages how data is stored, accessed, and manipulated, translating actions from design classes into tangible operations within the software system. Important functions of the "BankDatabase" implementation class include:

• Data Storage: Maintaining up-to-date records of all account information.
• Data Retrieval: Fetching account details as necessary for transaction processing.
• Data Security: Implementing safety protocols for protecting sensitive account information.

The "BankDatabase" class ensures precise and efficient handling of account data. It forms the backbone of the system's ability to execute and verify financial transactions securely and accurately.