Fancy Bread

To go along with my previous woolgathering on the correlation between a database schema and a class package, here is another observation regarding class inheritance and sub/supertype tables. In object modeling, we describe the relationship between a subclass and superclass as "is a". The same goes for tables in a data model, where the subtype "is a" supertype. The obvious benefit of using inheritance in object modeling is code reuse. When we add, remove or alter a method of the superclass, the change is automatically inherited by the subclass. In a data model the benefit of using subtypes is arguable. The benefit are that your model better represents the domain, reduces data duplication and (depending on the extent of your normalization) eliminates NULL values. The trade-off is that you are thereafter required to use joins when reading records and transactions when creating, updating or deleting records.

Read more...

When generating object models, I prefer to package related classes together. For instance, a Calendar would have the following classes: calendar.Calendar calendar.CalendarDAO calendar.CalendarService calendar.CalendarGateway Since my controller or view will never invoke methods on my CalenderDAO or CalendarGateway directly, I can secure the methods in those classes by setting access="package". Another subtle benefit is that the component files are organized in a single folder...

Read more...