Database Reference
In-Depth Information
23.2 Overview of Object-Oriented Database
Management Systems
In a truly object-oriented DBMS (OO DBMS), the following concepts hold (for more
details, see the references):
•
An object type is a concept or thing about which data is to be
stored, and a set of operations is to be defined.
•
An object is an instance of an object type.
•
An operation is a set of actions to be performed on an object.
•
A method specifies the way an operation is to be performed.
•
Encapsulation is the packaging of data structure and operations,
typically into a class. The internal structure of the class is hidden
from the outside, and only members (member functions) of the
class have access to it.
•
A subclass may inherit properties (structure or operations from
a subclass. Also a class may be comprised of several component
classes).
•
Polymorphism is the phenomenon where a given object or
operation may take on a different form, depending on the context
of usage.
•
Objects communicate by sending messages to each other. These
messages are managed via events; an object therefore responds to
events.
23.3 Challenges for Object-Oriented Database
Management Systems
A number of challenges stand in the way of achieving purely object-oriented DBMSs,
some of which have been articulated in [Date, 2004]. Figure
23-2
provides a brief
summary of these challenges.
