2. INTRODUCTION
• OBJECT :
• REAL WORLD ENTITIES
• HEART OF OBJECT ORIENTED APPROACH
• OBJECT ORIENTATION:
• VIEWING AND MODELLING THE WORLD OR SYSTEM AS A SET OF INTERACTING
&INTERRELATED OBJECTS.
• OBJECT ORIENTED MODELLING:
• FOCUSES ON THE DESIGNING OF OBJECT ORIENTED SYSTEMS.
• MODEL:
• IT CAN BE DEFINED AS AN ABSTRACTION OF SOMETHING BEFORE IT IS ACTUALLY
DEVELOPED ,INSTALLED OR PUT INTO PRACTICE.
• A MODEL IS AN ABSTRACTION OF SOMETHING FOR THE PURPOSE OF UNDERSTANDING IT
BEFORE BUILDING IT.
3. ELEMENTS OF OODM
OBJECTS: THE REAL WORLD ENTITIES AND SITUATIONS ARE
REPRESENTED AS OBJECTS IN THE OODM.
ATTRIBUTES AND METHOD: EVERY OBJECT HAS CERTAIN
CHARACTERISTICS.THESE ARE REPRESENTED USING ATTRIBUTES.THE
BEHAVIOUR OF THE OBJECT IS REPRESENTED USING METHODS.
CLASS: SIMILAR ATTRIBUTES AND METHODS ARE GROUPED TOGETHER
USING A CLASS. AN OBJECT CAN BE CALLED AS AN INSTANCE OF THE
CLASS.
INHERITANCE: A NEW CLASS CAN BE DERIVED FROM THE
ORIGINAL CLASS. THE DERIVED CLASS CONTAINS ATTRIBUTES AND
METHODS OF THE ORIGINAL CLASS AS WELL AS ITS OWN.
4.
5. FEATURES WHICH DISTINGUISH OODM FROM
TRADITIONAL DATABASE SYSTEMS
GENERIC PROPERTIES:THERE SHOULD BE AN INHERITANCE
RELATIONSHIP WITH MANY NUMBER OF CLASSES AND
SUBCLASSES.
ABSTRACTION: OBJECTS,CLASSES AND SUPER CLASSES ARE TO
BE GENERATED BY CLASSIFICATION, GENERALIZATION,
ASSOCIATION AND AGGREGATION.
ADHOC QUERIES: USERS CAN HAVE ANY SPATIAL OPERATION TO
OBTAIN SPATIAL RELATIONSHIPS OF GEOGRAPHIC OBJECTS
USING SOME CONCISE ‘ HIGH LEVEL’ LANGUAGES.
6. ADVANTAGES
THEY ARE MORE EFFICIENT TO MANAGE THE COMPLEX RELATIONSHIPS
BETWEEN OBJECTS THROUGH AN EASY MAINTENANCE AND
UPDATING.FOR EXAMPLE, A LINE MAY BE A BOUNDARY OF LAND OR
PROPERTY, A ROAD EDGE, OR SOMETHING ELSE. IN AN OODM, IT NEEDS
TO BE UPDATED ONLY ONCE , WHILE IN OTHER DATABASE SYSTEMS IT
REQUIRES MULTIPLE UPDATING OPERATIONS.
BECAUSE OF ITS INHERITANCE PROPERTY, WE CAN RE-USE THE
ATTRIBUTES AND FUNCTIONALITIES
IT REDUCES THE COST OF MAINTAINING THE SAME DATA MULTIPLE TIMES
ALSO, THESE INFORMATION ARE ENCAPSULATED AND,THERE IS NO FEAR
BEING MISUSED BY OTHERS OBJECTS
SINCE EACH CLASS BINDS ITS ATTRIBUTES AND ITS FUNCTIONALITY, IT IS
SAME AS REPRESENTING THE REAL WORLD OBJECT.
7. DISADVANTAGES
In comparison to RDBMSs the use of OODBMS is still relatively limited. This
means that we do not yet have the level of experience that we have with
traditional systems.
Also there is a resistance to the acceptance of the technology. While the
OODBMS is limited to a small niche market, this problem will continue to exist.
The increased functionality provided by the OODBMS (such as the illusion of a
single-level storage model, pointer swizzling, version management, and schema
evolution) makes the system more complex than that of traditional DBMSs. In
complexity leads to products that are more expensive and more difficult to use.
Currently, OODBMSs do not provide adequate security mechanisms. The user
cannot grant access rights on individual objects or classes.
of the most significant issues that face OODBMS vendors is the competition
posed by the RDBMS and the emerging ORDBMS products. These products
have an established user base with significant experience available.
