3.04_The ''include'' Dependency

Summary

This video explains the 'include' dependency in use case diagrams, a necessary relationship where one use case depends on another to be complete. It uses an online purchasing example to illustrate how the 'Make a Purchase' use case relies on the 'Verify Credit Card' use case. The include dependency is used when a specific step in one use case is required by others, streamlining the process of writing use cases. The included use case is conventionally placed to the right of the invoking use case in diagrams to avoid clutter.

Takeaways

• 🔄 The 'include' dependency in use case diagrams indicates a necessary relationship between two use cases.
• 📝 The invoking use case depends on the included use case to be complete.
• ➡️ The relationship is shown with a dotted dependency arrow labeled 'include'.
• 💳 An example is an online purchase system where 'make a purchase' depends on 'verify credit card'.
• 📌 The direction of the dependency arrow shows the dependency of one use case on the other.
• ⏳ Use the 'include' dependency when you know exactly when the invoking use case requires the included use case.
• 🏦 In scenarios like an ATM system, verifying the balance could be an included use case for multiple use cases (e.g., 'withdraw cash', 'transfer funds').
• ✍️ Including use cases saves effort in writing multiple steps repeatedly by defining a reusable included use case.
• 📐 In diagrams, the included use case is conventionally placed to the right of the invoking use case.
• ⚠️ Avoid cluttering diagrams with too many include relationships; use them effectively in written documentation for clarity.

Q & A

What is the include dependency in use case diagrams?

The include dependency in use case diagrams indicates a necessary relationship between two use cases, where the invoking use case depends on the included use case to be complete.

How do you represent an include dependency in a use case diagram?

An include dependency is represented by a dotted arrow pointing from the invoking use case to the included use case, and the arrow is labeled with the type of dependency, such as 'include.'

What does the direction of the dependency arrow signify in a use case diagram?

The direction of the dependency arrow shows which use case depends on the other. In an include dependency, the arrow points from the invoking use case to the included use case, indicating the invoking use case relies on the included one.

Can you provide an example of an include dependency?

Yes, for example, in an online purchasing application, the 'Make a Purchase' use case depends on the 'Verify Credit Card' use case. The 'Make a Purchase' use case includes the 'Verify Credit Card' use case as part of its process to reach its goal.

When should you use the include dependency in a use case diagram?

You should use the include dependency when you know exactly when the invoking use case requires the included use case, and the steps of the included use case clearly represent a necessary step in the invoking use case.

Why is the include dependency useful in written use cases?

The include dependency is useful in written use cases because it allows you to reuse the steps of an included use case in multiple other use cases, saving time and reducing redundancy in writing the steps repeatedly.

Can you provide an example where an included use case is shared among different invoking use cases?

Yes, in an ATM system, the 'Verify Balance' use case may be included in multiple use cases, such as 'Withdraw Cash' and 'Transfer Funds,' as both require verifying the balance.

How does using the include dependency save time in writing use cases?

Using the include dependency allows you to write the steps of a commonly used function, like 'Verify Balance,' once as a separate use case and include it in multiple other use cases, instead of writing the same steps repeatedly.

Where should the included use case appear in relation to the invoking use case in a diagram?

The included use case should always appear to the right of the invoking use case in a use case diagram as a visual convention.

Will you always draw the include relationship explicitly in diagrams?

Not always. Drawing every include relationship can clutter the diagram, so it's often better to write the include dependency in the use case text to save steps and keep the diagram clear.