Object Oriented Analysis and Design

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  • Topic: Unified Modeling Language, Use case, Use case diagram
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  • Published : February 8, 2013
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OBJECT ORIENTED ANALYSIS AND DESIGN

UNIT 1
INTRODUCTION TO OBJECT ORIENTATION
Object Orientation is a term used to describe the object – oriented(OO) method of building software. In an OO approach, the data is treated as the most important element and it cannot flow freely around the system. Restrictions are placed on the number of units that can manipulate the data. This approach binds the data and the methods that will manipulate the data closely and prevents the data from being inadvertently modified. The following figure shows the method1, method2, method3, and method4.

The ‘object’ forms the basis around which the following properties revolve: 1. Encapsulation
2. Abstraction, Implementation Hiding
3. Inheritance, dynamic binding, po lymorphism
4. Overriding and overloading
Encapsulation:
In Object Orientation, a class is used as a unit to group related attributes and operations together. The outside world can interact with the data stored in the variables that represent the attribut es of the class only through the operations of that class. Thus, the operations act as interfaces of the object of the class with the outside world.

For example, consider the class Employee with attributes empID, empName and dateOfJoining with is given below

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What is OOAD?
Object-oriented analysis and design (OOAD) is a software engineering approach that models a system as a group of interacting objects. Each object represents some entity of interest in the system being modeled, and is characterised by its class, its state (data elements), and its behavior. Various models can be created to show the static structure, dynamic behavior, and runtime deployment of these collaborating objects. There are a number of different notations for representing these models, such as the Unified Modeling Language (UML). Object-oriented analysis (OOA) applies object -modelling techniques to analyze the functional requirements for a system. Object -oriented design (OOD) elaborates the analysis models to produce implementation specifications. OOA focuses on what the system does, OOD on how the system does it.

Object-oriented systems
An object-oriented system is composed of objects. The behavior of the system results from the collaboration of those objects. Collaboration between objects involves them sending messages to each other. Sending a message differs from calling a function in that when a target object receives a message, it itself decides what function to carry out to service that message. The same message may be implemented by many different functions, the one selected depending on the state of the target object.

The implementation of "message sending" varies depending on the architecture of the system being modeled, and the location of the objects being communicated with. Object-oriented analysis
Object-oriented analysis (OOA) looks at the problem domain, with the aim of producing a conceptual model of the information that exists in the area being analyzed . Analysis models do not consider any implementation constraints that might exist, such as concurrency, distribution, persistence, or how the system is to be built. Implementation constraints ar e dealt during object oriented design (OOD). Analysis is done before the Design[citation needed]. The sources for the analysis can be a written requirements statement, a formal vision document, interviews with stakeholders or other interested parties. A system may be divided into multiple domains, representing different business, technological, or other areas of interest, each of which are analyzed separately.

The result of object -oriented analysis is a description of what the system is functionally required to do, in the form of a conceptual model. That will typically be presented as a set of use cases, one or more UML class diagrams, and a number of interaction diagrams. It may also include some kind of user interface mock-up. The purpose of...
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