Object Oriented Analysis And Design-

IT0207III SemesterUNIT-IV

Object oriented design process 1.Apply design axioms to design classes 1.1 Refine and complete the static UML

class diagram 1.2 Iterate and refine again 2. Design the access layer 2.1 create mirror classes 2.2 Identify access layer class

relationships 2.3 simplify classes and their

relationships 2.4 Iterate and refine again 3. Design the view layer classes 4. Iterate and refine the whole design

corollariesCorollary 1 Uncoupled design with less information contentCorollary 2 Single processCorollary 3 Large number of simple classesCorollary 4 Strong mappingCorollary 5 StandardizationCorollary 1 Design with inheritance

Object –oriented design axioms

Axiom 1.The independence axiom Maintain the independence of

componentsAxiom 2. The information axiom Minimize the information content

of the design

Designing Classes

Designing classes: The process 1. Apply design axioms to design

classes, their attributes,methods,associations, structures and protocols.

1.1 Refine and complete the static UML class diagram

1.2 Iterate and refine

Refining attributes

Attributes types 1. Single –value attributes 2. Multiplicity or multivalue attributes 3. References to another object

Attributes presentation : + public visibility # protected visibility - private visibility

Designing methods Several methods constructor destructor conversion method copy method attribute set attribute get I/O methods

OODBMS

Rules that satisfy OO system*System must support complex objects*object identity must be supported *object must be encapsulated * System must support types or classes* System must support inheritance* must avoid premature binding* System must be computationally complete* System must be extensible

-continuation Second rule

*Must be persistent * Must be able to manage very large databases*Must accept concurrent users* Must be able to recover from hardware and software*Data query must be simple

Designing access layer classesAccess layer performs two major tasks

* Translate the request* Translate the result

The process1. Mirror the business class

2. Define relationships 3. Simplify classes and relationships

4. Iterate and refine

Designing View layer1. Macro level UI design process2. Micro level UI design activities 2.1 Designing the view layer objects

by applying design axioms and corollaries2.2 Prototyping the view layer interface

3. Testing the usability and user satisfaction

4. Refining and iterating the design

View macro process

1. Define relationships among the view (interface) objects

2. Iterate and refine

View layer Micro process Apply micro-level UI design rules and

corollaries to develop the UI

Iterate and refine

Review Questions How would you differentiate good design from bad design? what is the basic activity in designing an application? Why is a large number of simple classes better than a small number of

complex classes? How can encapsulation, modularization and polymorphism Why are people not utilizing reusability? How would you decide a subdividing your classes into a hierarchy of

super and subclasses. What are the challenges in designing with inheritance?

How do you distinguish transient data from Persistent data? What is a DBMS? What is a relational database? explain tuple, primary key and foreign

key. Is a persistent object the same as a DBMS? What are the differences? What is a database schema? What is the difference between a schema

and meta -data? What is DDL? What is a distributed database? What is concurrency control? What is shareability? What is a concurrency policy?

Bibliography Object oriented system development by

Ali Brahami Object oriented methodology by Booch A text book on UML by Srimathi