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7 5-94-101

  1. 1. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 94ISSN (Online): A Comparison Between Five Models Of Software Engineering Nabil Mohammed Ali Munassar1 and A. Govardhan2 1 Ph.D Student of Computer Science & Engineering Jawahrlal Nehru Technological University Kuktapally, Hyderabad- 500 085, Andhra Pradesh, India 2 Professor of Computer Science & Engineering Principal JNTUH of Engineering College, Jagityal, Karimnagar (Dt), A.P., India Abstract increased recently which results in the difficulty ofThis research deals with a vital and important issue in computer enumerating such companies. During the previous fourworld. It is concerned with the software management processes decades, software has been developed from a tool used forthat examine the area of software development through the analyzing information or solving a problem to a product indevelopment models, which are known as software development itself. However, the early programming stages havelife cycle. It represents five of the development models namely, created a number of problems turning software anwaterfall, Iteration, V-shaped, spiral and Extreme programming.These models have advantages and disadvantages as well. obstacle to software development particularly thoseTherefore, the main objective of this research is to represent relying on computers. Software consists of documents anddifferent models of software development and make a programs that contain a collection that has beencomparison between them to show the features and defects of established to be a part of software engineeringeach model. procedures. Moreover, the aim of software engineering isKeywords: Software Management Processes, Software to create a suitable work that construct programs of highDevelopment, Development Models, Software Development Life quality.Cycle, Comparison between five models of Software Engineering.1. Introduction Computer Science ClientNo one can deny the importance of computer in our life,especially during the present time. In fact, computer hasbecome indispensible in todays life as it is used in manyfields of life such as industry, medicine, commerce, Theories Computer Function Problemseducation and even agriculture. It has become animportant element in the industry and technology ofadvanced as well as developing countries. Now a days,organizations become more dependent on computer intheir works as a result of computer technology. Computer The Software engineeringis considered a time- saving device and its progress helpsin executing complex, long, repeated processes in a veryshort time with a high speed. In addition to using Tools and techniques to solve problemscomputer for work, people use it for fun andentertainment. Noticeably, the number of companies thatproduce software programs for the purpose of facilitating Fig. 1 Explanation of software engineering of offices, administrations, banks, etc, has
  2. 2. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 95ISSN (Online): 1694-0814www.IJCSI.org2. Software Process Models concern.A software process model is an abstract representation of a The pure waterfall lifecycle consists of several non-process. It presents a description of a process from some overlapping stages, as shown in the following figure. Theparticular perspective as: model begins with establishing system requirements and1. Specification. software requirements and continues with architectural2. Design. design, detailed design, coding, testing, and maintenance.3. Validation. The waterfall model serves as a baseline for many other4. Evolution. lifecycle models.General Software Process Models are1. Waterfall model: Separate and distinct phases of System Requirements specification and development.2. Prototype model. Software Requirements3. Rapid application development model (RAD).4. Evolutionary development: Specification, development and validation are interleaved. Architectural Design5. Incremental model.6. Iterative model. Detailed Design7. Spiral model.8. Component-based software engineering : The system is assembled from existing components. CodingThere are many variants of these models e.g. formal Testingdevelopment where a waterfall-like process is used, butthe specification is formal that is refined through several Maintenancestages to an implementable design[1]. Fig. 2 Waterfall Model[4].3. Five Models RequirementsA Programming process model is an abstract Definitionrepresentation to describe the process from a particularperspective. There are numbers of general models forsoftware processes, like: Waterfall model, Evolutionarydevelopment, Formal systems development and Reuse- System andbased development, etc. This research will view the Software Designfollowing five models :1. Waterfall model.2. Iteration model.3. V-shaped model. Implementation and Unit Testing4. Spiral model.5. Extreme model.These models are chosen because their featurescorrespond to most software development programs. Integration and System Testing3.1 The Waterfall ModelThe waterfall model is the classical model of softwareengineering. This model is one of the oldest models and is Operation andwidely used in government projects and in many major Maintenancecompanies. As this model emphasizes planning in earlystages, it ensures design flaws before they develop. In Fig. 3 Waterfall model[2].addition, its intensive document and planning make it The following list details the steps for using the waterfallwork well for projects in which quality control is a major
  3. 3. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 96ISSN (Online): 1694-0814www.IJCSI.orgmodel: starting coding. There is no overlap between stages. In1 System requirements: Establishes the components real-world development, however, one can discover issues for building the system, including the hardware during the design or coding stages that point out errors or requirements, software tools, and other necessary gaps in the requirements. components. Examples include decisions on hardware, such as plug-in boards (number of The waterfall method does not prohibit returning to an channels, acquisition speed, and so on), and decisions earlier phase, for example, returning from the design phase on external pieces of software, such as databases or to the requirements phase. However, this involves costly libraries. rework. Each completed phase requires formal review and extensive documentation development. Thus, oversights2 Software requirements: Establishes the expectations made in the requirements phase are expensive to correct for software functionality and identifies which system later. requirements the software affects. Requirements analysis includes determining interaction needed with Because the actual development comes late in the process, other applications and databases, performance one does not see results for a long time. This delay can be requirements, user interface requirements, and so on. disconcerting to management and customers. Many people3 Architectural design: Determines the software also think that the amount of documentation is excessive framework of a system to meet the specific and inflexible. requirements. This design defines the major components and the interaction of those components, Although the waterfall model has its weaknesses, it is but it does not define the structure of each instructive because it emphasizes important stages of component. The external interfaces and tools used in project development. Even if one does not apply this the project can be determined by the designer. model, he must consider each of these stages and its relationship to his own project [4].4 Detailed design: Examines the software components defined in the architectural design stage and produces  Advantages : a specification for how each component is 1. Easy to understand and implement. implemented. 2. Widely used and known (in theory!). 3. Reinforces good habits: define-before- design,5 Coding: Implements the detailed design design-before-code. specification. 4. Identifies deliverables and milestones. 5. Document driven, URD, SRD, … etc. Published6 Testing: Determines whether the software meets the documentation standards, e.g. PSS-05. specified requirements and finds any errors present in 6. Works well on mature products and weak teams. the code.7 Maintenance: Addresses problems and enhancement  Disadvantages : requests after the software releases. 1. Idealized, doesn’t match reality well. 2. Doesn’t reflect iterative nature of exploratoryIn some organizations, a change control board maintains development.the quality of the product by reviewing each change made 3. Unrealistic to expect accurate requirements soin the maintenance stage. Consider applying the full early in project.waterfall development cycle model when correcting 4. Software is delivered late in project, delays discoveryproblems or implementing these enhancement requests. of serious errors. 5. Difficult to integrate risk management.In each stage, documents that explain the objectives and 6. Difficult and expensive to make changes todescribe the requirements for that phase are created. At the documents, ”swimming upstream”.end of each stage, a review to determine whether the 7. Significant administrative overhead, costly for smallproject can proceed to the next stage is held. Your teams and projects [6].prototyping can also be incorporated into any stage from  Pure Waterfallthe architectural design and after. This is the classical system development model. It consistsMany people believe that this model cannot be applied to of discontinuous phases:all situations. For example, with the pure waterfall model, 1. Concept.the requirements must be stated before beginning the 2., and the complete design must be stated before 3. Architectural design.
  4. 4. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 97ISSN (Online): 1694-0814www.IJCSI.org4. Detailed design. Risk reduction spirals can be added to the top of the5. Coding and development. waterfall to reduce risks prior to the waterfall phases. The6. Testing and implementation. waterfall can be further modified using options such as prototyping, JADs or CRC sessions or other methods of Table 1: Strengths & Weaknesses of Pure Waterfall requirements gathering done in overlapping phases [5]. Strengths Weaknesses 3.2 Iterative Development  Inflexible The problems with the Waterfall Model created a demand  Minimizes planning overhead since it can for a new method of developing systems which could be done up front.  Only the final phase provide faster results, require less up-front information, produces a non- and offer greater flexibility. With Iterative Development, documentation  Structure minimizes deliverable. the project is divided into small parts. This allows the wasted effort, so it development team to demonstrate results earlier on in the works well for process and obtain valuable feedback from system users. technically weak or  Backing up to address mistakes is Often, each iteration is actually a mini-Waterfall process inexperienced staff. with the feedback from one phase providing vital difficult. information for the design of the next phase. In a variation of this model, the software products, which are produced Pure Waterfall Summary at the end of each step (or series of steps), can go intoThe pure waterfall model performs well for products with production immediately as incremental releases.clearly understood requirements or when working withwell understood technical tools, architectures andinfrastructures. Its weaknesses frequently make itinadvisable when rapid development is needed. In thosecases, modified models may be more effective. Modified WaterfallThe modified waterfall uses the same phases as the purewaterfall, but is not based on a discontinuous basis. Thisenables the phases to overlap when needed. The purewaterfall can also split into subprojects at an appropriatephase (such as after the architectural design or detaileddesign). Table 2: Strengths & Weaknesses of Modified Waterfall Strengths Weaknesses  More flexible than the  Milestones are more Fig. 4 Iterative Development. pure waterfall model. ambiguous than the pure waterfall.  If there is personnel continuity between the  Activities performed 3.3 V-Shaped Model phases, documentation in parallel are subject can be substantially to miscommunication Just like the waterfall model, the V-Shaped life cycle is a reduced. and mistaken sequential path of execution of processes. Each phase assumptions. must be completed before the next phase begins. Testing  Implementation of easy is emphasized in this model more than the waterfall areas does not need to  Unforeseen model. The testing procedures are developed early in the wait for the hard ones. interdependencies can create problems. life cycle before any coding is done, during each of the phases preceding implementation. Requirements begin the Modified Waterfall Summary life cycle model just like the waterfall model. Before
  5. 5. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 98ISSN (Online): Requirements System Test Systemdevelopment is started, a system test plan is created. The Planning Testingtest plan focuses on meeting the functionality specified inrequirements gathering.The high-level design phase focuses on systemarchitecture and design. An integration test plan is created High Level Integration Integrationin this phase in order to test the pieces of the software Design Test Testing Planningsystems ability to work together. However, the low-leveldesign phase lies where the actual software componentsare designed, and unit tests are created in this phase aswell. Low Level Unit Test Unit Design Planning TestingThe implementation phase is, again, where all codingtakes place. Once coding is complete, the path ofexecution continues up the right side of the V where thetest plans developed earlier are now put to use. Implementation Advantages1. Simple and easy to use.2. Each phase has specific deliverables. Fig. 6 V-Shaped Life Cycle Model[7].3. Higher chance of success over the waterfall model due to the early development of test plans during the life cycle. 3.4 Spiral Model4. Works well for small projects where requirements are easily understood. The spiral model is similar to the incremental model, with more emphases placed on risk analysis. The spiral model has four phases: Planning, Risk Analysis, Engineering and Evaluation. A software project repeatedly passes through these phases in iterations (called Spirals in this model). The baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed. Each subsequent spiral builds on the baseline spiral. Requirements are gathered during the planning phase. In the risk analysis phase, a process is undertaken to identify risk and alternate solutions. A prototype is produced at the end of the risk analysis phase. Software is produced in the engineering phase, along with testing at the end of the phase. The evaluation phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral. In the spiral model, the angular component represents progress, and the radius of the spiral represents cost. Fig. 5 V-Model [3]  Advantages Disadvantages 1. High amount of risk analysis. 2. Good for large and mission-critical projects.1. Very rigid like the waterfall model. 3. Software is produced early in the software life cycle.2. Little flexibility and adjusting scope is difficult and expensive.  Disadvantages3. Software is developed during the implementation phase, 1. Can be a costly model to use. so no early prototypes of the software are produced. 2. Risk analysis requires highly specific expertise.4. This Model does not provide a clear path for problems 3. Project’s success is highly dependent on the risk found during testing phases [7]. analysis phase. 4. Doesn’t work well for smaller projects [7].
  6. 6. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 99ISSN (Online): Spiral model sectors under which the system would produce win-lose or lose-1. Objective setting :Specific objectives for the phase are lose outcomes for some stakeholders. identified. 3. Identify and Evaluate Alternatives: Solicit2. Risk assessment and reduction: Risks are assessed and suggestions from stakeholders, evaluate them with respect activities are put in place to reduce the key risks. to stakeholders win conditions, synthesize and negotiate3. Development and validation: A development model candidate win-win alternatives, analyze, assess, resolve for the system is chosen which can be any of the win-lose or lose-lose risks, record commitments and areas general models. to be left flexible in the projects design record and life cycle plans.4. Planning: The project is reviewed and the next phase 4. Cycle through the Spiral: Elaborate the win conditionsof the spiral is planned [1]. evaluate and screen alternatives, resolve risks, accumulate appropriate commitments, and develop and execute downstream plans [8]. 3.5 Extreme Programming An approach to development, based on the development and delivery of very small increments of functionality. It relies on constant code improvement, user involvement in the development team and pair wise programming . It can be difficult to keep the interest of customers who are involved in the process. Team members may be unsuited to the intense involvement that characterizes agile methods. Prioritizing changes can be difficult where there are multiple stakeholders. Maintaining simplicity requires extra work. Contracts may be a problem as with other approaches to iterative development. Fig. 7 Spiral Model of the Software Process[1]. WinWin Spiral ModelThe original spiral model [Boehm 88] began each cycle ofthe spiral by performing the next level of elaboration ofthe prospective systems objectives, constraints andalternatives. A primary difficulty in applying the spiralmodel has been the lack of explicit process guidance indetermining these objectives, constraints, and alternatives.The Win-Win Spiral Model [Boehm 94] uses the theoryW (win-win) approach [Boehm 89b] to converge on a Fig. 8 The XP Release Cyclesystems next-level objectives, constraints, andalternatives. This Theory W approach involves identifyingthe systems stakeholders and their win conditions, and  Extreme Programming Practicesusing negotiation processes to determine a mutually Incremental planning: Requirements are recorded onsatisfactory set of objectives, constraints, and alternatives Story Cards and the Stories to be included in a release arefor the stakeholders. In particular, as illustrated in the determined by the time available and their relative priority.figure, the nine-step Theory W process translates into the The developers break these stories into developmentfollowing spiral model extensions: "Tasks".1. Determine Objectives: Identify the system life-cycle Small Releases: The minimal useful set of functionalitystakeholders and their win conditions and establish initial that provides business value is developed first. Releases ofsystem boundaries and external interfaces. the system are frequent and incrementally add2. Determine Constraints: Determine the conditions functionality to the first release.
  7. 7. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 100ISSN (Online): 1694-0814www.IJCSI.orgSimple Design: Enough design is carried out to meet the 4. Test case construction is a difficult and specializedcurrent requirements and no more. skill [6].Test first development: An automated unit testframework is used to write tests for a new piece offunctionality before functionality itself is implemented. 4. Conclusion and Future WorkRefactoring: All developers are expected to re-factor thecode continuously as soon as possible code improvements After completing this research , it is concluded that :are found. This keeps the code simple and maintainable. 1. There are many existing models for developingPair Programming: Developers work in pairs, checking systems for different sizes of projects andeach other’s work and providing support to do a good job. requirements.Collective Ownership: The pairs of developers work on 2. These models were established between 1970 andall areas of the system, so that no islands of expertise 1999.develop and all the developers own all the code. Anyone 3. Waterfall model and spiral model are used commonlycan change anything. in developing systems.Continuous Integration: As soon as work on a task is 4. Each model has advantages and disadvantages for thecomplete, it is integrated into the whole system. After any development of systems , so each model tries tosuch integration, all the unit tests in the system must pass. eliminate the disadvantages of the previous modelSustainable pace: Large amounts of over-time are notconsidered acceptable as the net effect is often to reduce Finally, some topics can be suggested for future works:code quality and medium term productivity.On-site Customer: A representative of the end-user of the 1. Suggesting a model to simulate advantages that aresystem (the Customer) should be available full time for the found in different models to software processuse of the XP team. In an extreme programming process, management.the customer is a member of the development team and is 2. Making a comparison between the suggested modelresponsible for bringing system requirements to the team and the previous software processes managementfor implementation. models. 3. Applying the suggested model to many projects to XP and agile principles ensure of its suitability and documentation to explain1. Incremental development is supported through small, its mechanical work. frequent system releases.2. Customer involvement means full-time customer REFERENCES engagement with the team. [1] Ian Sommerville, "Software Engineering", Addison3. People not process through pair programming, Wesley, 7th edition, 2004. collective ownership and a process that avoids long [2] CTG. MFA – 003, "A Survey of System Development working hours. Process Models", Models for Action Project: Developing4. Change supported through regular system releases. Practical Approaches to Electronic Records Management5. Maintaining simplicity through constant refactoring of and Preservation, Center for Technology in Government code [1]. University at Albany / Suny,1998 . [3] Steve Easterbrook, "Software Lifecycles", University Advantages of Toronto Department of Computer Science, 2001.1. Lightweight methods suit small-medium size projects. [4] National Instruments Corporation, "Lifecycle Models",2. Produces good team cohesion. 2006 , Emphasises final product. [5] JJ Kuhl, "Project Lifecycle Models: How They Differ4. Iterative. and When to Use Them",2002 Test based approach to requirements and quality assurance. [6] Karlm, "Software Lifecycle Models, KTH,2006 . [7] Rlewallen, "Software Development Life Cycle Disadvantages Models", 2005 , Difficult to scale up to large projects where [8] Barry Boehm, "Spiral Development: Experience, documentation is essential. Principles, and Refinements", edited by Wilfred J.2. Needs experience and skill if not to degenerate into Hansen, 2000 . code-and-fix.3. Programming pairs is costly. Nabil Mohammed Ali Munassar was born in Jeddah, Saudi Arabia in 1978. He studied Computer Science at University of Science and Technology, Yemen from 1997 to 2001. In 2001 he
  8. 8. IJCSI International Journal of Computer Science Issues, Vol. 7, Issue 5, September 2010 101ISSN (Online): 1694-0814www.IJCSI.orgreceived the Bachelor degree. He studied Master of InformationTechnology at Arab Academic, Yemen, from 2004 to 2007. Now rdhe Ph.D. Student 3 year of CSE at Jawaharlal NehruTechnological University (JNTU), Hyderabad, A. P., India. He isworking as Associate Professor in Computer Science &Engineering College in University Of Science and Technology,Yemen. His area of interest include Software Engineering, SystemAnalysis and Design, Databases and Object OrientedTechnologies.Dr.A.Govardhan: received Ph.D. degree in Computer Scienceand Engineering from Jawaharlal Nehru Technological Universityin 2003, M.Tech. from Jawaharlal Nehru University in 1994 andB.E. from Osmania University in 1992. He is Working as aPrincipal of Jawaharlal Nehru Technological University, Jagitial. Hehas published around 108 papers in various national andinternational Journals/conferences. His research of interestincludes Databases, Data Warehousing & Mining, InformationRetrieval, Computer Networks, Image Processing, SoftwareEngineering, Search Engines and Object Oriented Technologies.