Coupling and Abstraction  Oracle Tips by Burleson Consulting

High Performance Data Warehousing

Database Architectures For The 1990s

COUPLING OF DATA AND BEHAVIOR 

The Oracle8 engine allows for the direct coupling of a database entity (a table or object) with a set of predefined behaviors. In this fashion, calls to Oracle will be made by specifying an object name and the method associated with the object. For example:

CUSTOMER.add_new("Jones", 123, "other parms");

This call tells Oracle to invoke the add_new procedure attached to the customer object using the supplied parms. As you might expect, this new way of invoking database calls has important ramifications for the developers and DBA staff.

For developers, applications will become SQL-less and will consist of calls to stored procedures. Of course, this has the important benefit of making applications portable across platforms, while also making it very easy to find and reuse code. In addition, because each method is encapsulated and tested independently, the pretested methods can be assembled with other methods without worry of unintended side effects.

For DBAs, the coupling of data with behaviors will dramatically change the way DBAs perform database administration tasks. Instead of only managing data and tables, the Oracle8 DBA will also be responsible for managing objects and the methods associated with each object. These new object administrator functions will need to be defined so developers know the functions and parameters of each method.

Abstraction

Abstraction within Oracle8 is defined as the conceptual (not concrete) existence of classes within the database. For example, a database may have a class hierarchy that includes classes without objects. A military database may contain the conceptual entities of division, battalion, squadron, and platoon. The function of the database is to track the platoons, and the entity classes of division, battalion, and squadron may not have any associated objects. This is not to say that abstract classes have no purpose. When a class is defined, it is associated with behaviors, which in turn will be inherited by each object in the platoon class. From a database perspective, there will be no instances of any objects except platoon, but higher levels in the class hierarchy will contain behaviors which the platoon objects inherit.