Summary

Key takeaways

1. We started the chapter with an introduction to reference properties. If an object has references to another object as its values, that’s its reference property. These reference properties can be single-valued (Committee::chair) or multi-valued (Book::authors). We learned how to represent this relationship using UML diagrams.

2. We learned the importance of referential integrity—that there’s a referenced object in the database for every reference. We learned about the checks we need to put into place to implement referential integrity and how to manage the change dependencies using an appropriate deletion policy.

3. We learned how to represent unidirectional associations using reference properties. We also learned how those associations help represent an information design model that contains the necessary information for a database design model and an OOP model. Then, we found out how to turn a non-directed association into a directed one.

4. Next, we learned how to remove explicit associations from design models. We turned all non-directional associations into unidirectional ones by determining the ownership of their ends. We then saw how to convert these associations into reference properties.

5. Finally, we learned how to render the UI’s reference properties using the appropriate widgets. To render single-valued reference properties, we can use single-selection lists or radio button groups. For multi-valued reference properties, we can use a multi-selection list or a check box group in the UI.