OBJECTORIENTED DBMS

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OBJECT-ORIENTED DBMS
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Structured Object Oriented Approaches

• Structured approach long history,
  well-documented
• ERD - modeling data
• DFD - modeling process
• Tools System Architect, Visible Analysis
• OO approach new, offer benefits such as soft
  reuse
• Class Diagram - modeling data
• USE-Case diagram - system functionalities
• Tools Rational Rose

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OO Concepts

• Classes
• Class is a group of objects that have similar
  attributes (properties) and behavior
• All objects in class have similar attributes and
  they perform similar operations
• E.g. all pupils in a students class will have the
  same attributes (not attribute values) such as
  name and address.

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• An object is a structure that encapsulates (or
  packages) both data and methods.
• The data (also called properties) describes the
  attributes of the object while methods (also
  called operations, services, functions or
  procedures) describe its behavior.

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An Object with Attributes and Methods
Employee
Objects Name
EmpNo EmpName Pay
Objects Attribute
ModifyInfo ComputePay
Objects Method
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Encapsulation

• Encapsulation means packaging both the data
  objects and method together
• Only methods within an object are allowed to
  modify the objects attribute (data).
• The data and details of the methods of an object
  are hidden from other objects data and methods
  i.e. the external methods (belonging to other
  objects) cannot modify other objects attribute.

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Class Hierarchy
Person
Superclass (also known as base, parent or
ancestor class)
Student
Lecturer
Subclass (also known as child or derived class)
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• Multilevel Class Hierarchy

Person
Superclass
Employee
Student
Base class
Foreign employee
Local employee
Part Time Student
Full Time student
Base class
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Inheritance

• Inheritance is the property that when classes are
  arranged in a hierarchy, a derived class can
  inherit (automatically) the properties (
  attributes) and behaviors (methods) of its parent
  or base class.

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e.g.
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Inherited attributes and methods
Person
Name Age Sex
Initialize Add modify
Derived Properties Name Age Sex Initialize
Add modify
Employee
Student
EmpNo Pay
StudNo Course
ComputePay
ChangeInfo
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OO Databases

• In OO data management (OODM) , each object in the
  system has an identity that is internal to the
  data stored within the object
• There is no concept of primary key
• OODBMS maintains an external identifier for each
  object, which is not accessible to any object,
  function or application
• The identity of the object does not change

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Types of Methods
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Advantages of OODBMS

• Enriched modeling capabilities closely model
  the real world object
• Extensibility allows to develop new abstract
  data types using existing data types
• More expressive query
• Suitable for advance DB applications

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Disadvantages of OODBMS

• Lack of experience
• Lack of standards
• Lack of view mechanism
• Inadequate security

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• Despite of its capability, OODBMS did not gain so
  much popularity and not widely accepted.
• Reasons why organizations are reluctant to use
  OODBMS
• Existing investment
• High switching cost
• Using two methodologies in the same organization
  can be expensive
• Staff training cost

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• THE END