Database Reference
In-Depth Information
5.7 Database Design via the UML Model
Database design with the UML model is somewhat similar to database design with the
E-R model. The points of divergence relate to the differences in notation between the
two approaches as well as the semantic jargon used. The rules that prescribe bow to treat
various types of relationships (section 3.5.4) are still applicable. However, in order to be
consistent with object-oriented (OO) terminology, you would replace the term relation
(or entity) with the term object type. With this in mind, we may construct a procedure for
database design via the UML model as follows:
Figure 5-12.
Database Design Procedure Using the UML Model
Note
: Due to the inherent behavior of typical OO software products, introducing
primary keys and foreign keys into object types (implemented as classes) as we
have prescribed, may be unnecessary. In a purely OO environment, these links are
automatically introduced by the OO software and implemented as pointers — a feature
called encapsulation; however, they are internal and cannot be tracked by the user. For
this reason, many OO pundits argue that normalization and data independence run
counter to inheritance and encapsulation. The debate as to when to use an OO database
versus a relational database and vice versa, is likely to be ongoing for some time into the
foreseeable future. It will be revisited in chapter 23.
