IM 341

Business Systems Analysis

Chapter 8

Object Modeling

I. Introduction to Object modeling

A. Object-oriented Analysis (OOA) – techniques used to:

1. Study existing objects to see if they can be reused or adapted for new uses a

2. Define new or modified objects that will be combined with existing objects into useful business computing applications

B. Object Modeling - a technique for identifying objects within the systems environment and relationships between those objects

II. System Concepts For Object Modeling to

A. The Object

1. Object - something it is or is capable of being seen, touched, or otherwise sensed, and about which users store data and associate behavior

2. Attributes - the data represent characteristics of interest about object

3. Instance - the values for the attributes that describe a specific person, place, thing, oriented.

4. Behavior - refers to those things that the object can do and that correspond to functions that act on the object’s data/attributes; commonly referred to as a method or service

5. Encapsulation - packaging of several items together into one unit

B. Classes, Generalization, Specialization

1. Class - a several objects that share common attributes and behavior; sometimes referred to as an object class

2. Inheritance - methods and/or attributes defined in object class can be inherited or reused by another object class

3. Generalizations/Specialization - a technique where attributes in behaviors, to several types of object classes are grouped into their own class, or Supertype. The attributes and methods of the supertype object class are then inherited by those object classes.

4. Supertype - an object whose instances store attributes that are common to one or more class subtypes of the object

5. Subtype - an object class whose instances inherit some common attributes from a class supertype and then add other attributes unique to the instance of subtype

C. Object/Class Relationships - a natural business association that exists between one or more objects/classes: the customer places zero or more orders, an order is placed by one and only one customer

Multiplicity - the minimum and maximum number of occurrences of one object/class for a single occurrence of the related object/class

D. Messages and Message Sending - a message is passed when one object invokes one or more of another object’s methods (behaviors) to request information or some action

E. Polymorphism - "many forms" - the same named behavior may be completed differently for different objects/classes. A door and a window may both be closed, but they both close differently. A window may slide downward while a door swings shut, but both actions close the objects.

III. The Process of Object Modeling - to general activities of Object-Oriented Analysis:

1. Find and identify the business objects

2. Organize the objects and identify their relationships

(This is all of this chapter that will be covered in this class)