Comparison of the Waterfall, Spiral, and Prototype SDLC Models

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<p>Running Head: THE WATERFALL, SPIRAL, AND PROTOTYPE SDLC MODELS 1</p> <p>2THE WATERFALL, SPIRAL, AND PROTOTYPE SDLC MODELS</p> <p>A Comparison of the Waterfall, Spiral, and Prototype SDLC ModelsTeresa J. RothaarWilmington University</p> <p>A Comparison of the Waterfall, Spiral, and Prototype SDLC ModelsIntroductionThere are numerous software/systems development lifecycle (SDLC) models. According to Ruparelia (2010), each SDLC model can be classified in one of three categories: linear, iterative, or a combination of both. Linear models are sequential; each stage automatically leads into the next, and stages are not revisited or repeated. Iterative models are structured around the idea that the SDLC is a continuous process, and each stage will be revisited multiple times during the life of the project. A combined model is an iterative model with a finish line: It acknowledges that, at some point, there will be no more need to revisit any of the stages (p. 8).This paper will compare and contrast three popular SDLC models: waterfall, spiral, and prototype.The Waterfall ModelThe term waterfall refers to a methodology as well as a model; software engineers often use the term interchangeably (C. Seifer, personal communication, March 18, 2015). There are actually two waterfall models: the traditional, linear model and a newer, iterative model. Each model has five steps: requirements analysis, design, implementation, testing, and maintenance (Maheshwari &amp; Jain, 2012, p. 286).In the traditional waterfall model, each step flows into the other sequentially. While some splash back is permitted, the goal of the model is to move through each phase and onto the next without repeating, with an emphasis on planning, time schedules, target dates, budgets and implementation of an entire system at one time (Maheshwari &amp; Jain, 2012, p. 286). This method is highly structured, with well-defined deliverables and milestones for each phase, which make it easy to understand. However, the tight structure of the original waterfall modelin particular, the need to consider and plan for every possible eventuality at the beginning of the projecthas caused it to fall out of favor in todays dynamic business environment. Often, the project sponsor may not know exactly what they want at the outset, or, in the case of a large project being done over a long period of time, something may change in the macro environment that requires changes to the project (Maheshwari &amp; Jain, 2012, p. 286).Enter the iterative waterfall model. The steps are the same as in the traditional waterfall method, but with testing and analysis at the end of each phase, which theoretically provides valuable feedback when moving into the next phase. Additionally, unlike in the traditional model, it is expected that phases will be repeated. The advantage of this model is that it is better suited to the dynamic world of modern software and systems development; however, it lacks the clear milestones of the original model and, thus, could be difficult to manage (Maheshwari &amp; Jain, 2012, p. 286-287).The Spiral ModelAmong the most flexible of SDLC models is the spiral model (Saxena &amp; Kaushik, 2013, p. 118), which is a combination of the traditional waterfall model and the prototype model (Khurana &amp; Gupta, 2012, p. 1516). It has four phases: requirements planning, risk analysis, development and testing, and planning the next iteration. At the end of the risk analysis phase, a prototype is produced, which is coded and tested in the third phase, then evaluated in the fourth phase; feedback from this iteration is used to plan the next one. The hallmark of the spiral model is its emphasis on risk analysis and mitigation, which makes it particularly suitable for very large, costly projects (Khurana &amp; Gupta, 2012, p. 1515-1516). Figure 1 (Aafrin, 2012) visually demonstrates the similarities and differences between the traditional waterfall and spiral models. The steps are very similar. However, while each step falls into the next when using waterfall, the spiral method keeps going around the spiral as many times as necessary. While the method is considered iterative, it can be used as a combination method, as eventually, the project will be finished and there will be no need to go through further iterations:</p> <p>Figure 1. A visual representation of the difference between the linear waterfall model and the iterative spiral model. The spiral model is not suitable for every project. Saxena and Kaushik (2013) note that, among other drawbacks, it is very expensive and highly complex; there is no specified finish line, and it can be difficult to determine when to stop going through the iterations; and it requires that project managers have a high level of expertise in risk management. Thus, they recommend that it be used only for large, highly complex, risky, and expensive projects (p. 118).The Prototype ModelAccording to Maheshwari and Jain (2012), the prototype (or prototyping) model isnt solely a standalone model, though it can be used as one; it is an approach that can be incorporated into any SDLC model (p. 287). For example, as discussed above, prototyping is an important part of the spiral model. Shukla and Saxena (2013) break the prototype model down into six steps: requirements gathering; initial designing of the prototype; building the prototype; having the client evaluate the prototype; refining the prototype; and finally, building the end product (p. 19). As Figure 2 (ISTQB Exam Certification, 2012) illustrates, prototyping is a linear method, like waterfall, with a beginning and an end:</p> <p>Figure 2. A diagram of the prototype model.Because it requires building a working model (which could end up being discarded), the prototype model is expensive; however, its not as expensive as the spiral model (Shukla &amp; Saxena, 2013, p. 19). Other advantages include the fact that the client gets to see a working model early in the project, which makes it easier for the client to make improvement suggestions, may make it easier to get the project funded, and mitigates risk. However, costs can be high. The development process can be slow, and as mentioned above, once feedback is received from the client regarding the initial prototype, it may end up being useless. Additionally, the prototype model encourages a lot of communication between the client and the developer; while this is helpful in ensuring the client is happy with the final product, a non-technical client may expect the moon and become upset when the developer cannot deliver on all requests as quickly and inexpensively as the client thinks they should (Saxena &amp; Kaushik, 2013, p. 119). Shukla and Saxena (2013) recommend using this method only for small projects (p. 19).ConclusionThis paper discussed three popular SDLC models; many more exist. All of them include phases for gathering requirements, performing a business analysis, designing the system, implementing the system, and performing QA testing (Mishra &amp; Dubey, 2013, p. 64). There is no one correct model; all of them do the same thing, but use different problem-solving approaches. The decision to choose one model over the other is dependent on the particular situation under which an individual project is being developed.</p> <p>ReferencesAafrin (2012). Waterfall Model vs. Spiral Model [Online image]. Retrieved from Exam Certification (2012). Prototyping Model [Online image]. Retrieved from, G., &amp; Gupta, S. (2012). Study &amp; Comparison of Software Development Life Cycle Models.International Journal of Research in Engineering &amp; Applied Sciences,2(2), 1513-1521. Retrieved from, S., &amp; Jain, D. C. (2012). A Comparative Analysis of Different Types of Models in Software Development Life Cycle. International Journal of Advanced Research in Computer Science and Software Engineering, 2(5), 285-290. Retrieved from, A., &amp; Dubey, D. (2013). A Comparative Study of Different Software Development Life Cycle Models in Different Scenarios. International Journal, 1(5), 64-69. Retrieved from, N. B. (2010). Software development lifecycle models. ACM SIGSOFT Software Engineering Notes, 35(3), 8-13., P., &amp; Kaushik, M. (2013). Advantages and Limitations of Different SDLC Models. International Journal For Technological Research In Engineering, 1(3), 117-121. Retrieved from, A. K., &amp; Saxena, A. (2013). Which Model is Best for the Software Project? A Comparative Analysis of Software Engineering Models. International Journal of Computer Applications, 76(11), 18-22.</p>


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