MY BOOK REVIEW

OBJECT ORIENTED ANALYSIS and DESIGN

Book Name

EDWARD YOURDON and CARL ARGILA

Author

QA 76.76 Y68 1996

Reference no.

CHAPTER 1

BACKGROUND: The Philosophy of Software Development

“Philosophy” may seem like an unusual word with which to start off a book of case studies on software development. However, the author, whose combined experience totals well over 1500 fortnights, during their careers dramatic changes in the commonly accepted “philosophy” of building software system when computing began 1950's programs were created using an ad hoc software development approach;each system was a unique, custom built intellectual product. There was no concept of reusability, interchangeability of parts, or, for what the matter, formal design. Although pioneering,this software system were to difficult to maintain or enhance. And each change to a system produce a system which was even more difficult to maintain or enhance!

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 (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 are dealt with during object-oriented design (OOD). Analysis is done before the Design.

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 case, one or more UML class diagram and a number of interaction diagramIt may also include some kind of user interfacemock-up.

Object-oriented design (OOD) transforms the conceptual model produced in object-oriented analysis to take account of the constraints imposed by the chosen architecture and any non-functional – technological or environmental – constraints, such as transaction throughput, response time, run-time platform, development environment, or programming language.

The concepts in the analysis model are mapped onto implementation classes and interfaces. The result is a model of the solution domain, a detailed description of how the system is to be built..

KEYPOINTS

the principles of Separation of Concerns distinguishes between essential requirements and implementation requirements.

Today's software development techniques can't scale up for the system of tomorrow.

The concept of object-oriented is very different than the traditional top-down functional decomposition approach.

Object-oriented techniques are an enabling technology for full software life cycle reuse.

An object is an independent,asynchronous,concurrent entity which knows things,does work and collaborates with other objects to perform the function of a system.

The object-oriented Analysis model has a five layers; we use a specific notation syntax to represent object, attributes,service and other object-oriented concept.

The Object-Oriented Design model has four component. It has the same structure as the OOA model

There is nothing more difficult to take in hand, more perilous to conduct or more uncertain in its success, than to take the lead in the introduction of a new order of things.

Niccollo Machiavelli

The prince, Ch 6