Ans. There are several advantages of Spiral model that makes it a realistic approach to development of large-scale systems and software, viz: 1) The spiral model promotes quality assurance through prototyping at each stage in system development. 2) The spiral model is a realistic approach to the development of large-scale software products because the software evolves as the process progresses. The developer and client better understand and react to risk at each evolutionary level. 3) The model uses prototyping as a risk reduction mechanism and allows for the development of prototypes at any stage of the evolutionary development.
4)It maintains a systematic stepwise approach like the classic life cycle model but incorporates it into an iterative framework that more reflect the real world. If employed correctly this model should reduce risk before they become problematic as consideration of technical risk are considered at all stages Spiral model is also known, as spiral life cycle model is a system development life cycle model used in information technology. This model of development combines the features of prototyping model and waterfall model. The spiral model is used for large, expensive and complicated project. •Presented by BARRY BOHEM in 1986 incorporating the project risk factor. •Designed in order to overcome the disadvantages of waterfall model. •The radial dimension represents the cumulative cost incurred in accomplishing the steps done so far and the angular dimension represents the progress made in completing each cycle of the spiral. •Each loop is a development stage. •Balance all the risk elements that is the high-risk element must be lowered. •The people concerned with the project complete each phase with a review. Different Phases of spiral model: 1) Planning: In this phase the objectives, alternatives and constraints of the project are determined or documented. The objectives and other specifications are fixed in order to decide which strategies or approaches to follow during the project life cycle. 2) Risk analysis: In this phase, all possible and available alternatives which can help in developing a cost effective project are analyzed and strategies are decided to use them. This phase has been added specially in order to identify and resolve all the possible risk in the project development. 3) Development: In this phase the actual development of the project is carried out. The output of this phase is passed through all the phases iteratively in order to obtain improvements in the same. 4) Assessment: In this phase, developed product is pass on to the customer in order to receive customer comments and suggestions, which can help in identifying and resolving potential problems or errors in the software development.