Distributed object Database Management Systems & Object Oriented Data Model

Distributed Object Database Management Systems

Fundamental Object Concepts & Models

An Object-Oriented DBMS (OODBMS) stores data as objects (like OOP) instead of tables.

Basic Concepts

Concept	Description
Object	Instance with data + behaviour
Class	Blueprint of objects
Attributes	Data values
Methods	Functions/operations
Encapsulation	Data hiding

Object Model Diagram


Class: Student
--------------------
| id              |
| name            |
--------------------
| getDetails()    |
--------------------

Features

Combines database + object-oriented programming
Supports complex data types
Reduces impedance mismatch

Object Distributed Design

Designing object databases across multiple distributed sites.

Key Considerations

Object fragmentation
Object replication
Object allocation

Distributed Object Design


Object Class
     ↓
Fragmentation
     ↓
Distribution across Nodes

Goals

Efficient access
Reduced communication cost
Scalability

Architectural Issues in OODBMS

Key Issues

Issue	Description
Object Distribution	Where objects are stored
Object Identity	Unique ID across the system
Query Processing	Efficient retrieval
Concurrency Control	Multiple object access
Transaction Management	ACID support

Object Management

Handling creation, storage, update, and deletion of objects.

Tasks

Task	Description
Object Creation	Create instances
Object Access	Retrieve objects
Object Update	Modify data
Object Deletion	Remove objects

Distributed Object Storage

Storing objects across multiple nodes.

Techniques

Technique	Description
Fragmentation	Split objects
Replication	Copy objects
Clustering	Store related objects together

Storage Diagram


Node1 → Object A
Node2 → Object B
Node3 → Object A (Replica)

Object Query Processing

Retrieving objects using object-oriented query languages (OQL).

Steps


Query → Decomposition → Optimization → Execution → Result

Example (OQL-like)


SELECT s.name FROM Student s WHERE s.marks > 80;

Challenges

Complex object relationships
Distributed execution

Object-Oriented Data Model

Inheritance

Mechanism where the child class inherits properties of the parent class.

Example


Person
  |
Student (inherits Person)

Types

Single inheritance
Multiple inheritance

Advantages

Code reuse
Easy maintenance

Object Identity

Each object has a unique identifier (OID) independent of its values. Example: Two objects may have the same data but different OIDs.

Diagram


Object1 → OID = 101
Object2 → OID = 102

Persistent Programming Language

Languages that allow objects to persist beyond program execution.

Examples

Java (with persistence frameworks)
C++ (with object DB support)

Features

Store objects permanently
Automatic object retrieval

Persistence of Objects

Ability of objects to exist after the program ends.

Types

Type	Description
Persistent	Stored permanently
Transient	Temporary

Persistence Diagram


Program End
   |
Objects Stored in DB
   |
Reused Later

Comparison: OODBMS vs ORDBMS

Comparison Table

Feature	OODBMS	ORDBMS
Data Model	Object-based	Relational + Objects
Structure	Classes	Tables
Relationships	Object references	Foreign keys
Query Language	OQL	SQL
Performance	Good for complex data	Better for structured data

Explanation

OODBMS

Best for complex applications (CAD, multimedia)

ORDBMS

Extension of relational DB with object features

Combined Architecture


Application (OOP)
       |
OODBMS Layer
       |
Distributed Object Storage
       |
Multiple Nodes

Important Exam Questions

Short Questions

Define object identity
What is inheritance?
What is persistence?

Long Questions

Explain the object-oriented data model
Describe the distributed object DBMS architecture
Compare OODBMS and ORDBMS

Case-Based Questions

Design an object database for a student system
Explain object storage in a distributed environment

Final Summary

OODBMS → stores data as objects
Inheritance → reuse properties
Object Identity → unique ID
Persistence → long-term storage
OODBMS vs ORDBMS → object vs relational extension

Distributed object Database Management Systems & Object Oriented Data Model