7 - Indira Gandhi Centre for Atomic Research

An OODB combines object oriented programming principles with database management
principles. Object oriented programming concepts such as encapsulation, polymorphism
and inheritance are enforced along with regular database management concepts such as the
Atomicity, Consistency, Isolation and Durability (ACID properties). OODB is a system
while supporting all the functionality of a relational database system (including queries,
transactions, backup and recovery mechanisms), also offers an Object oriented
programming language interface, user defined data types, object identifiers and the ability
to manage objects persistently.
3. Object Oriented Data Model (OODM)
Object oriented data model represents real-world entities as objects. Each object’s attributes
and methods implementation is hidden from other object. A unique object ID identifies
each object. Classes inherits all properties of their super classes.T he OODM is different
from E-R and Relational model in the sense that the OODM object has additional properties
like behavior, inheritance and encapsulation. Such features make OODM more close to real
world entities. OODM classes allow the implementation of Abstract Data Types (ABT).
The ABT is used to create new data types and is a powerful modeling tool. In relational
model the relationship among entities is established through a common attribute. OODM in
contrast uses object ID to establish relation among objects.
Objects can be used persistently and transiently. Persistent instances of objects are
automatically and transparently stored by the OODB. Transient instances exist only while
the application based on the OODB is running. Locking and transaction mechanisms
guarantee security and integrity for multi-user update operations.
4. The Object Data Management Standard (ODMG Standard)
ODMG was founded in 1991 to define the criteria for OODBs, to provide a feature list for
OODB comparisons and to introduce standards into the OODB world. Most major OODB
vendors are members of this group. The ODMG has published several documents called
´ODMG Standards.’ The first version of this standard appeared in 1993. The current
version is ODMG 2.0. This document defines an object model, an object definition
language (ODL), an object query language (OQL) and interfaces for the programming
languages C++, Smalltalk and Java.
5. Object Definition Language (Odl) and Object Query Language (OQL)
ODL describes the database schema, i.e. the hierarchy of object classes, their elements and
methods. The ODL is independent of the programming language (C++, Java, Smalltalk). A
pre-processor translates the schema into class definitions for the programming language.
The ODMG-OQL is based on O 2 SQL (which in turn is based on SQL 92). In addition to
SQL-style queries, OQL can be used to query complex types of data. It can make use of the
methods in classes. The OQL does not support recursive queries.
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