Object-Oriented Database Management Systems (ODBMS)

1
Object-Oriented Database Management Systems
(ODBMS)

• By Wendy Wooters
• CS157B

2
ODBMS Outline

• Definition
• 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.

4
Why use ODBMS?
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 http//www.service-architecture.com/object
-oriented-databases
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.

• Object-oriented DB model.
• Application and database use same object-oriented
  model.
• Uses persistent programming languages.

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.

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

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)

• 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

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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

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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.

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Java ODB Example

• import org.odmg.
• import java.util.Collection
• Implementation impl new com.vendor.odmg.Implemen
  tation()
• 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() )

• 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 http//www.service-architecture.com/object
-oriented-databases
15
Conclusion

• Definition
• Persistent Programming Languages
• Object-Oriented Concepts
• Advantages and Disadvantages of ODBMS
• Example Code