Object-oriented analysis and design (OOAD) is a technical approach for analyzing and designing an application, system, or business by applying

object-oriented programming Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pr ...

, as well as using visual modeling throughout the software development process to guide stakeholder communication and product quality. OOAD in modern software engineering is typically conducted in an iterative and incremental way. The outputs of OOAD activities are analysis models (for OOA) and design models (for OOD) respectively. The intention is for these to be continuously refined and evolved, driven by key factors like risks and business value.

History

In the early days of object-oriented technology before the mid-1990s, there were many different competing methodologies for software development and

object-oriented modeling Object-oriented modeling (OOM) is an approach to modeling an application that is used at the beginning of the software life cycle when using an object-oriented approach to software development. The software life cycle is typically divided up into ...

, often tied to specific

Computer Aided Software Engineering Computer-aided software engineering (CASE) is the domain of software tools used to design and implement applications. CASE tools are similar to and were partly inspired by Computer-Aided Design (CAD) tools used for designing hardware products. CAS ...

(CASE) tool vendors. No standard notations, consistent terms and process guides were the major concerns at the time, which degraded communication efficiency and lengthened learning curves. Some of the well-known early object-oriented methodologies were from and inspired by gurus such as

Grady Booch Grady Booch (born February 27, 1955) is an American software engineer, best known for developing the Unified Modeling Language (UML) with Ivar Jacobson and James Rumbaugh. He is recognized internationally for his innovative work in software archit ...

James Rumbaugh James E. Rumbaugh (born August 22, 1947) is an American computer scientist and object-oriented methodologistIvar Jacobson Ivar Hjalmar Jacobson (born 1939) is a Swedish computer scientist and software engineer, known as major contributor to UML, Objectory, Rational Unified Process (RUP), aspect-oriented software development and Essence. Biography Ivar Jacobson w ...

(the ''Three Amigos''), Robert Martin,

Peter Coad Peter Coad (born December 30, 1953) is a software entrepreneur and author of books on programming. He is notable for his role in defining what have come to be known as the UML colors, a color-coded notation chiefly useful for adding breadth and ...

Sally Shlaer Sally hashim Shlaer (December 3, 1938 – November 12, 1998) was an American mathematician, software engineer and methodologist,Stephen Mellor, and

Rebecca Wirfs-Brock Rebecca J. Wirfs-Brock (born 1953 in Portland, Oregon) is an American software engineer and consultant in object-oriented programming and object-oriented design, the founder of the information technology consulting firm Wirfs-Brock Associates, an ...

. In 1994, the ''Three Amigos'' of Rational Software started working together to develop the

Unified Modeling Language The Unified Modeling Language (UML) is a general-purpose, developmental modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system. The creation of UML was originally m ...

(UML). Later, together with

Philippe Kruchten Philippe Kruchten (born 1952) is a Canadian software engineer, and Professor of Software Engineering at University of British Columbia in Vancouver, Canada, known as Director of Process Development (RUP) at Rational Software, and developer of the ...

and Walker Royce (eldest son of Winston Royce), they have led a successful mission to merge their own methodologies, OMT,

OOSE Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pr ...

and

Booch method The Booch method is a method for object-oriented software development. It is composed of an object modeling language, an iterative object-oriented development process, and a set of recommended practices. The method was authored by Grady Booch wh ...

, with various insights and experiences from other industry leaders into the

Rational Unified Process The Rational Unified Process (RUP) is an iterative software development process framework created by the Rational Software Corporation, a division of IBM since 2003. RUP is not a single concrete prescriptive process, but rather an adaptable proce ...

(RUP), a comprehensive iterative and incremental process guide and framework for learning industry best practices of software development and project management. Since then, the

Unified Process The Unified Software Development Process or Unified Process is an iterative and incremental software development process framework. The best-known and extensively documented refinement of the Unified Process is the Rational Unified Process (RU ...

family has become probably the most popular methodology and reference model for object-oriented analysis and design.

Overview

The software life cycle is typically divided up into stages going from abstract descriptions of the problem to designs then to code and testing and finally to deployment. The earliest stages of this process are analysis and design. The analysis phase is also often called "requirements acquisition". Waterfall model revised

In some approaches to software development—known collectively as waterfall models—the boundaries between each stage are meant to be fairly rigid and sequential. The term "waterfall" was coined for such methodologies to signify that progress went sequentially in one direction only, i.e., once analysis was complete then and only then was design begun and it was rare (and considered a source of error) when a design issue required a change in the analysis model or when a coding issue required a change in design. The alternative to waterfall models are iterative models. This distinction was popularized by

Barry Boehm Barry William Boehm (May 16, 1935 – August 20, 2022) was an American software engineer, distinguished professor of computer science, industrial and systems engineering; the TRW Professor of Software Engineering; and founding director of the Cen ...

in a very influential paper on his Spiral Model for iterative software development. With iterative models it is possible to do work in various stages of the model in parallel. So for example it is possible—and not seen as a source of error—to work on analysis, design, and even code all on the same day and to have issues from one stage impact issues from another. The emphasis on iterative models is that software development is a knowledge-intensive process and that things like analysis can't really be completely understood without understanding design issues, that coding issues can affect design, that testing can yield information about how the code or even the design should be modified, etc. Although it is possible to do object-oriented development using a waterfall model, in practice most object-oriented systems are developed with an iterative approach. As a result, in object-oriented processes "analysis and design" are often considered at the same time. The object-oriented paradigm emphasizes modularity and re-usability. The goal of an object-oriented approach is to satisfy the "openclosed principle". A module is open if it supports extension, or if the module provides standardized ways to add new behaviors or describe new states. In the object-oriented paradigm this is often accomplished by creating a new subclass of an existing class. A module is closed if it has a well defined stable interface that all other modules must use and that limits the interaction and potential errors that can be introduced into one module by changes in another. In the object-oriented paradigm this is accomplished by defining methods that invoke services on objects. Methods can be either public or private, i.e., certain behaviors that are unique to the object are not exposed to other objects. This reduces a source of many common errors in computer programming. The software life cycle is typically divided up into stages going from abstract descriptions of the problem to designs then to code and testing and finally to deployment. The earliest stages of this process are analysis and design. The distinction between analysis and design is often described as "what vs. how". In analysis developers work with users and domain experts to define what the system is supposed to do. Implementation details are supposed to be mostly or totally (depending on the particular method) ignored at this phase. The goal of the analysis phase is to create a functional model of the system regardless of constraints such as appropriate technology. In object-oriented analysis this is typically done via use cases and abstract definitions of the most important objects. The subsequent design phase refines the analysis model and makes the needed technology and other implementation choices. In object-oriented design the emphasis is on describing the various objects, their data, behavior, and interactions. The design model should have all the details required so that programmers can implement the design in code.

Object-oriented analysis

The purpose of any analysis activity in the software life-cycle is to create a model of the system's functional requirements that is independent of implementation constraints. The main difference between object-oriented analysis and other forms of analysis is that by the object-oriented approach we organize requirements around objects, which integrate both behaviors (processes) and states (data) modeled after real world objects that the system interacts with. In other or traditional analysis methodologies, the two aspects: processes and data are considered separately. For example, data may be modeled by ER diagrams, and behaviors by

flow charts A flowchart is a type of diagram that represents a workflow or process. A flowchart can also be defined as a diagrammatic representation of an algorithm, a step-by-step approach to solving a task. The flowchart shows the steps as boxes of va ...

structure chart A structure chart (SC) in software engineering and organizational theory is a chart which shows the breakdown of a system to its lowest manageable levels.IRS (2008) "Configuration Management" In: ''IRS Resources Part 2. Information Technology Chap ...

s. Common models used in OOA are use cases and

object model In computing, object model has two related but distinct meanings: # The properties of objects in general in a specific computer programming language, technology, notation or methodology that uses them. Examples are the object models of ''Java'', ...

Use case In software and systems engineering, the phrase use case is a polyseme with two senses: # A usage scenario for a piece of software; often used in the plural to suggest situations where a piece of software may be useful. # A potential scenario ...

s describe scenarios for standard domain functions that the system must accomplish. Object models describe the names, class relations (e.g. Circle is a subclass of Shape), operations, and properties of the main objects. User-interface mockups or prototypes can also be created to help understanding.

Object-oriented design

During object-oriented design (OOD), a developer applies implementation constraints to the conceptual model produced in object-oriented analysis. Such constraints could include the hardware and

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

platforms, the performance requirements, persistent storage and transaction, usability of the system, and limitations imposed by budgets and time. Concepts in the analysis model which is technology independent, are mapped onto implementing classes and interfaces resulting in a model of the solution domain, i.e., a detailed description of ''how'' the system is to be built on concrete technologies. Important topics during OOD also include the design of

software architecture Software architecture is the fundamental structure of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations. ...

s by applying

architectural pattern An architectural pattern is a general, reusable solution to a commonly occurring problem in software architecture within a given context. The architectural patterns address various issues in software engineering, such as computer hardware perform ...

s and

design patterns ''Design Patterns: Elements of Reusable Object-Oriented Software'' (1994) is a software engineering book describing software design patterns. The book was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, with a foreword ...

with the object-oriented design principles.

Object-oriented modeling

Object-oriented modeling (OOM) is a common approach to modeling applications, systems, and business domains by using the object-oriented paradigm throughout the entire development life cycles. OOM is a main technique heavily used by both OOD and OOA activities in modern software engineering. Object-oriented modeling typically divides into two aspects of work: the modeling of dynamic behaviors like business processes and

use cases In software and systems engineering, the phrase use case is a polyseme with two senses: # A usage scenario for a piece of software; often used in the plural to suggest situations where a piece of software may be useful. # A potential scenario i ...

, and the modeling of static structures like classes and components. OOA and OOD are the two distinct abstract levels (i.e. the analysis level and the design level) during OOM. The Unified Modeling Language (UML) and

SysML The Systems Modeling Language (SysML) is a general-purpose modeling language for systems engineering applications. It supports the specification, analysis, design, verification and validation of a broad range of systems and systems-of-systems. S ...

are the two popular international standard languages used for object-oriented modeling. The benefits of OOM are: Efficient and effective communication Users typically have difficulties in understanding comprehensive documents and programming language codes well. Visual model diagrams can be more understandable and can allow users and stakeholders to give developers feedback on the appropriate requirements and structure of the system. A key goal of the object-oriented approach is to decrease the "semantic gap" between the system and the real world, and to have the system be constructed using terminology that is almost the same as the stakeholders use in everyday business. Object-oriented modeling is an essential tool to facilitate this. Useful and stable abstraction Modeling helps coding. A goal of most modern software methodologies is to first address "what" questions and then address "how" questions, i.e. first determine the functionality the system is to provide without consideration of implementation constraints, and then consider how to make specific solutions to these abstract requirements, and refine them into detailed designs and codes by constraints such as technology and budget. Object-oriented modeling enables this by producing abstract and accessible descriptions of both system requirements and designs, i.e. ''models'' that define their essential structures and behaviors like processes and objects, which are important and valuable development assets with higher abstraction levels above concrete and complex source code.

References

External links

* Articl
Object-Oriented Analysis and Design with UML and RUP
an overview (also about CRC cards). * Applying UML �
Object Oriented Analysis & Design
tutorial * OOAD & UML Resource website and Forums �
Object Oriented Analysis & Design with UML

Software Requirement Analysis using UML
article by Dhiraj Shetty. *Articl
Object-Oriented Analysis in the Real World
{{DEFAULTSORT:Object-Oriented Analysis And Design Object-oriented programming Software design