Use cases are a powerful tool for capturing and communicating the functional requirements of a system. They describe how a user interacts with the system to achieve a specific goal, and what the system does in response. Use cases can help you to:
- Understand the needs and expectations of your users
- Define the scope and boundaries of your system
- Validate your assumptions and design decisions
- Test your system against real scenarios
However, to create effective use cases, you need to follow some best practices. One of them is to keep all related transactions separate when you identify use cases. A transaction is a sequence of actions that either succeeds or fails as a whole. For example, withdrawing money from an ATM is a transaction that involves entering your PIN, selecting an amount, receiving cash, and getting a receipt.
Keeping related transactions separate means that you should not mix different transactions in the same use case. For example, you should not write a use case that covers both withdrawing money and checking your balance from an ATM. Instead, you should write two separate use cases, one for each transaction.
Why is this important? Here are some reasons:
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Clarity and Simplicity
Keeping related transactions separate makes your use cases clearer and simpler to understand. Each use case should have a single, clear, and concise goal that reflects the user’s intention. Mixing different transactions in the same use case can make it confusing and ambiguous. For example, what is the main goal of a use case that covers both withdrawing money and checking your balance? Is it to withdraw money or to check your balance? How do you know when the use case is completed?
By separating related transactions, you can avoid these problems and make your use cases more focused and coherent. Each use case will have a well-defined goal, preconditions, postconditions, main flow, and alternative flows. This will make it easier for you and your stakeholders to read, understand, and validate your use cases.
Modularity and Reusability
Keeping related transactions separate also makes your use cases more modular and reusable. Modularity means that each use case is independent and self-contained, without depending on other use cases. Reusability means that you can use the same use case in different contexts and scenarios, without having to rewrite or duplicate it.
By separating related transactions, you can achieve both modularity and reusability. Each use case will have its own inputs, outputs, and logic, without relying on other use cases. This will make it easier for you to maintain and update your use cases, as well as to reuse them in different combinations and variations.
For example, if you have separate use cases for withdrawing money and checking your balance from an ATM, you can reuse them in different scenarios, such as:
- A user wants to withdraw money and then check their balance
- A user wants to check their balance and then withdraw money
- A user wants to withdraw money only
- A user wants to check their balance only
You can also extend or modify your use cases without affecting other use cases. For example, if you want to add a feature that allows users to print their balance after withdrawing money, you can simply extend the use case for withdrawing money with an optional step, without changing the use case for checking balance.
Testability and Traceability
Finally, keeping related transactions separate improves the testability and traceability of your use cases. Testability means that you can easily verify that your system meets the functional requirements specified by your use cases. Traceability means that you can easily track the relationship between your requirements, design, implementation, and testing.
By separating related transactions, you can enhance both testability and traceability. Each use case will have its own test cases that cover all possible scenarios and outcomes. This will make it easier for you to test your system against your use cases, as well as to identify and fix any defects or errors.
Moreover, each use case will have its own unique identifier and name that reflects its goal. This will make it easier for you to trace your use cases throughout the development process, from requirements analysis to design to implementation to testing. You will be able to link your use cases with other artifacts, such as user stories, diagrams, code modules, test scripts, etc.
Conclusion
Use cases are a valuable technique for capturing and communicating the functional requirements of a system. However, to create effective use cases, you need to follow some best practices. One of them is to keep all related transactions separate when you identify use cases.
This will help you to:
- Make your use cases clearer and simpler
- Make your use cases more modular and reusable
- Make your use cases more testable and traceable
By doing so, you will be able to deliver a high-quality system that meets the needs and expectations of your users.