TRENDS IN DATABASE TECHNOLOGY - Database Design and Development: An Essential Guide for IT Professionals - page 633

Semantic Data Models

Generalization
Aggregation

OBJECT-
ORIENTED
DATA
MODEL

Object-Orientation

Object identity
Encapsulation
Inheritance
Concurrency Control
Classes and Types
Data Security
Methods and Messages
Polymorphism
Extensibility

Figure 20-7 Object-oriented data model.

Operation polymorphism. Overloading is a form of operation polymorphism. With
a method with one name you can have different operations performed based on the
context.

Inclusion polymorphism. Relates to a method defined in one class and inherited by
a subclass.

Parametric polymorphism. Uses a type as a parameter in generic type or class dec-
larations.

Object-Oriented Data Model

When we discussed the design of a relational database, we considered the creation
of a logical model. You studied the various components that make up the logical
data model for traditional database systems. We also went through the steps for
creating the logical model.
The detailed steps to create an object-oriented data model are beyond the scope
of our discussions here. Let us just consider the features of an object-oriented data
model. Basically, an object-oriented data model must represent the structure and
meanings of objects defined in the context of object orientation. Figure 20-7 cap-
tures the essence of an object-oriented data model.

OODB An object-oriented data model defines an object-oriented database
(OODB). Object-oriented databases combine database capabilities with object
orientation. Figure 20-8 illustrates the type of integration present in OODBs.
Vendors take different approaches for integrating object orientation and data-
base functionality. Here are the main methods:

• Add database capabilities to object-oriented programming languages.
• Include functions provided by object orientation to existing database
languages.