Identifying Classes in Object-Oriented Analysis: Classification and Noun Phrase Approach, Schemes and Mind Maps of Computer Vision

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12/24/22 11

Object Analysis:

Classification

Dr. Santosh Kumar Swain

Associate Professor School Of Computer Engineering KIIT , Bhubaneswar. 12/24/22 1

Introduction

• (^) OOA is a process by which we can identify classes that play a role in achieving system goals and requirements
• (^) Various Approaches for identifying the classes
• (^) Classification: is the process of checking to see if an object belongs to a category or a class, is regarded as a basic attribute of human nature. Example: Classifying the car

What is a Class?

• (^) A Class is a software template that defines the methods and variables to be included in a particular kind of Object.
• (^) Is a blue print used to create objects. As it is a blue print , at runtime it will not occupy any memory.
• (^) Examples : Animal, Human being, Automobiles

... Intelligent classification is intellectually hard work, and it best comes about through an incremental and iterative process Booch

Point To Remember Two Issues

• (^) A class is a specification of structure, behavior, and the description of an object.
• (^) Classification is more concerned with identifying classes than identifying the individual objects in a system.

The Challenge of Classification

• (^) Intelligent classification is intellectually hard work and may seem rather arbitrary.
• (^) Martin and Odell have observed in object-oriented analysis and design, that “In fact, an object can be categorized in more than one way.”

Noun Phrase Approach

• (^) Using this method, you have to read through the Use cases, interviews, and requirements specification carefully, looking for noun phrases.

Noun Phrase Strategy (Con’t)

• (^) Change all plurals to singular and make a list, which can then be divided into three categories. Relevent Classes (^) Fuzzy Classes Irrelevent Classes

Guidelines For Identifying Classes

• (^) The followings are guidelines for selecting classes in your application:
• (^) Look for nouns and noun phrases in the problem statement.
• (^) Some classes are implicit or taken from general knowledge.

Guidelines For Identifying Classes (Con’t)

• (^) All classes must make sense in the application domain.
• (^) Avoid computer implementation classes, defer it to the design stage.
• (^) Carefully choose and define class names.

Guidelines For Refining Classes (Con’t) Adjective Classes:

• (^) Does the object represented by the noun behave differently when the adjective is applied to it?

Guidelines For Refining Classes (Con’t)

• (^) If the use of the adjective signals that the behavior of the object is different, then make a new class.
• (^) For example, If Adult Membership and Youth Membership behave differently, than they should be classified as different classes.

Guidelines For Refining Classes (Con’t) Irrelevant Classes:

• (^) Each class must have a purpose and every class should be clearly defined and necessary.
• (^) If you cannot come up with a statement of purpose, simply eliminate the candidate class.

Identifying a list of candidate classes

• (^) Take a coherent, concise statement of the requirement of the system
• (^) Underline its noun and noun phrases, that is, identify the words and phases the denote things
• (^) This gives a list of candidate classes, which we can then modify to get an initial class list for the system