1. Object-Oriented Database Management Systems (ODBMS)
By Wendy Wooters
CS157B

2. ODBMS Outline Definition Persistent Programming Languages
Why
Who
Approaches
Persistent Programming Languages
Object-Oriented Concepts
Object
Class & Encapsulation
Inheritance & Polymorphism
Object Identifier (OID)
Advantages and Disadvantages
Example Code
Conclusion

3. What is an ODBMS?
Database that stores data elements as objects. Uses object-oriented concepts.
Object - like an entity in and E-R Diagram.
Employee
Name
Salary
Hired
SSN

4. Why use ODBMS? Complex data or relationship requirements
Product DB
Complex data or relationship requirements
Lack of unique, natural identification
Large numbers of many to many relationships
Access using traversals. Graph/Tree structure.
Frequent use of type codes such as those found in the relational schema
Source:

5. Who Uses ODBMS? Typical Applications for ODBMS:
Computer-aided design (CAD)
Computer-aided software engineering (CASE)
Multimedia databases
Images, video, games, etc.
Office automation systems (OIS)
Expert database systems

6. Approaches for ODBMS
Relational DB extended to use object-oriented concepts. (Object-relational DB)
DB is Relational
Programming language is object-oriented.
RDB
Application
Translation
Object-oriented DB model.
Application and database use same object-oriented model.
Uses persistent programming languages.
ODB
Application

7. Persistence Programming Languages
A programming language that directly manipulates persistent data in a database.
Persistent data exists after the program terminates.
Single program for application and data management. No translation from database to application programming needed.
Used with the object-oriented DB model approach.
ODB
Application

8. Object-Oriented Concepts Object
Object is an entity containing:
Variables/Attributes – Object Data
Relationships – References to other objects
Methods – Object Functions
Messages – Accessing Methods
Variables
Methods
Employee
SSN:int
Name:String
Hired:Date
Salary:double …
getSSN()
getName()
setName()
Relationships

9. Object-Oriented Concepts Class & Encapsulation
Public class Employee {
//Class Attributes
private int SSN;
private String name;
private Date hired;
private double salary; …
//Class Constructor
public Employee() {…}
//Class Accessor Methods
public int getSSN() {…}
public String getName() {…}
public Date getHired() {…}
public double getSalary() {…}
//Class Mutator Methods
public void setName(String newName) {…}
public void setHired(Date newHired) {…}
public void setSalary(double newSalary) {…} }
Class encapsulates the data structure and operations of the object.
Internals are hidden from the user.
User only knows available methods and how to call them.

10. Object-Oriented Concepts Inheritance & Polymorphism
Inheritance - A class (subclass) can inherit the characteristic of another class (superclass).
Example: Employee has inherited attributes and methods from Person.
Polymorphism - Each subclass object can respond differently to same message by overriding the superclass method. Example:
Person
Employee
Supplier
Customer
Subclass
Superclass

11. Object-Oriented Concepts Object Identifier
Object Identifier (OID) – The unique OID is maintained by the DBMS.
ODBMS - Generated automatically by the system. Example: Reference to Date object in the Employee object for the date hired.
RDBMS – Primary key. Example: SSN for Employee
Date
Employee

12. ODBMS Advantages Matches the object-oriented application design:
Reduces code, execution time and paging
Real world data model
Easier Navigation
Allows reusability of objects – generic objects can be used in many applications.
Manages Complex data types more efficiently.
Supports distributions of data across networks more efficiently.

13. ODBMS Disadvantages Still developing
Lack of accepted standards
Lack of development tools.
Change is more likely to occur in model
More complicated than the relational model. Takes longer to learn.
Not as efficient when data and relations are simple.

14. Java & ODB Example
import org.odmg.*;
import java.util.Collection;
Implementation impl = new com.vendor.odmg.Implementation();
Database db = impl.newDatabase();
Transaction txn = impl.newTransaction();
try {
db.open("addressDB", Database.OPEN_READ_WRITE);
txn.begin();
// perform query
OQLQuery query = new OQLQuery(
"select x from Person x where x.name = \“S. M. Lee\"");
Collection result = (Collection) query.execute();
Iterator iter = result.iterator();
// iterate over the results
while ( iter.hasNext() ) {
Person person = (Person) iter.next();
// do some addition processing on the person (now shown)
// now traverse to the address object and update its value
person.address.street = " th Avenue South"; }
txn.commit();
db.close();
//exception handling would go here ...
Example of how to access data in an ODB, using the ODMG Object Query Language (OQL):
Opens DB
Starts a transaction
Executes a query to find a Person object named “S. M. Lee”
Does additional processing on this Person object
Gets Address object of Person
Update street of Address object
Commit transaction
Close database
Source:

15. Conclusion Definition Persistent Programming Languages
Object-Oriented Concepts
Advantages and Disadvantages of ODBMS
Example Code