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As per the name, spiral model is a software development methodology that is arranged in a spiral shape. It was proposed by Barry Boehm and is mostly used to handle high risk and also large projects. The spiral model uses iterations, meaning similar steps that are repeated until the needs are satisfied. This methodology is suitable when requirements are not clear to the software developers. Prototypes are made in this methodology and given to the users to be tested to change the requirements to make sure it fulfills all the user requirements. Examples of systems that might utilize this methodology would be large systems like airport terminal systems, large information systems and so on. To further elaborate on the methodology, it is compared with several other commonly used methodologies in the table below.
Advantages and Disadvantages
Requires high amount of documentation
* Unable to move back a step| Table 1: Advantages and Disadvantages of Spiral, RAD and Waterfall models (self-made) The table above clearly illustrates all the advantages spiral model has. This model is proposed for the EasyRent Video to develop the e-commerce website for the said company because it will allow for fast development with very low risks. The spiral model allows highly customized systems to be created which will suit the company’s needs very well. Unlike the waterfall model which is slower and inflexible, the spiral model can create systems that are fully functional in a short time. Although RAD achieves similar goals, RAD is not recommended because it would not create a unique system for the company. By hiring a few skilled employees, the spiral model can be completed in very short time with the user being highly satisfied with the product because of the involvement of the users in the development lifecycle.
Using spiral model also reduces risk because risk management is one of the key steps in the spiral model. Steps would be taken to ensure risk to the company and the system be kept at a minimum so that unexpected events would not occur. In comparison to the waterfall model, the spiral model has the advantage of being flexible and adaptable to changes. The main difference between the two methodologies would be that waterfall technique gives higher emphasis on analysis while the spiral technique places more priority on the creation of the system before analysis. The waterfall technique is slower and does not involve much customer involvement. Moreover, the system that would be created based on the waterfall model for EasyRent Video would most likely not meet the requirements of the users. On the other hand, the spiral model would allow the users to have a system that suits all of their needs in shorter time.
Overview of Spiral model
Diagram 1: Example of spiral model
(Source: http://zone.ni.com/images/reference/en-XX/help/371361J-01/loc_eps_spiral_lifecycle.gif) The diagram above details several phases in the spiral model. The spiral model’s main purpose would be to develop highly customized systems within a short amount of time with relatively low risk. To implement the spiral method when developing the system for EasyRent Video, steps or phases are taken according to the table below.
Phases and Implementation of Spiral model
Based on the above table, EasyRent Video’s e-commerce website project would be started by researching the existing system, which is the store based selling system and the requirements for the website would be researched by using methods such as interviews, observation and questionnaires. The user requirements would then be used to determine an initial draft of the system with the major characteristics or features that the user would like to have in the system. After the initial draft is completed, schedules and tasks are arranged into development phases. Next, the first prototype is built according to the initial system draft which would be given to the user for evaluation. A fourfold procedure is initiated to create the second prototype. The first step out of the four would be to evaluate the first prototype according to the strengths, weaknesses and also the risk. Next, research would be done to find out the requirements of the second prototype.
The third step would be planning and designing the second prototype while the last step would be to construct and test the second prototype. After the second prototype is created, the user is brought in to access the situation. If the user finds the risk of continuing the project too high, he or she could immediately terminate the whole project. This step is included so that the company does not lose money to cost overruns or create a system that does not fulfill the company’s requirements.
The system then goes through another prototyping phase if necessary and a final prototype is created based on the fourfold procedure. Lastly, the final system is built according to the final prototype and implemented in the company. Continued maintenance and updates to the system are also implemented so that the system would function effectively. The above phases would provide a highly customized system that would be ready to use by the users at the end of the software development lifecycle. The spiral model would be highly recommended for its flexibility, low risk, high customization and also fast development.
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