1. Software Design Concepts 773.707 Spring 2002 Dr. Sothy Vignarajah Object Oriented Programming

2. Chapter 11 and Chapter 12 Objectives: Object-Oriented Model Object-Oriented Methodology Object-Oriented Analysis Object-Oriented Design Terminology

3. Object-Oriented Model The fundamental entity –the object receives and sends messages, performs computations and has a local state that can be modified. Problems are solved by sending messages to each other. The OO model is made up of 4 components: objects, messages, methods, and classes.

4. Object-Oriented Analysis Here we identify the abstractions of the problem domain by identifying: Objects Classes Attributes Methods relationships

5. OOD Define the problem – understand the structure of the problem space –Understanding is an iterative process. –As you go deeper into the problem you uncover new aspects of the problem which we may not have recognized before. –In real world projects, the problem space is described by some type of formal specifications.

6. Develop an informal strategy Once the highest levels of the problem is understood, create an informal strategy that parallels our view of the world.We first have an intuitive fell for the problem and then tighten up our understanding by evolving more formal descriptions – “it should be recognized that informality will always exist during the formulation of a specification” (Balzer, Goldman & Wile, 1978)

7. Formalize the strategy An informal strategy – extract the nouns which represent objects, along with qualifying adjectives which represent attributes of each object. As you select the noun phrases, you uncover several types of nouns: common nouns – names of classes of entities (tables, terminals, sensors, switches)

8. Formalize the strategy Contd. Mass nouns and units of measure – quality, activity, substance or a quantity – water, matter, fuel Proper nouns and nouns of direct reference – Name of a specific being or entity – nozzle-pressure sensor, my table, abort switch etc. (The first two identify abstract data types)