Spiral Model free essay sample

The spiral model combines the idea of iterative development (prototyping) with the systematic, controlled aspects of the waterfall model. It allows for incremental releases of the product, or incremental refinement through each time around the spiral. The spiral model also explicitly includes risk management within software development. Identifying major risks, both technical and managerial, and determining how to lessen the risk helps keep the software development process under control.The spiral model is based on continuous refinement of key products for requirements definition and analysis, system and software design, and implementation (the code). At each iteration around the cycle, the products are extensions of an earlier product. This model uses many of the same phases as the waterfall model, in essentially the same order, separated by planning, risk assessment, and the building of prototypes and simulations. Documents are produced when they are required, and the content reflects the information necessary at that point in the process. We will write a custom essay sample on Spiral Model or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page All documents will not be created at the beginning of the process, nor all at the end (hopefully). Like the product they define, the documents are works in progress. The idea is to have a continuous stream of products produced and available for user review. The spiral lifecycle model allows for elements of the product to be added in when they become available or known. This assures that there is no conflict with previous requirements and design. This method is consistent with approaches that have multiple software builds and releases and allows for making an orderly transition to a maintenance activity.Another positive aspect is that the spiral model forces early user involvement in the system development effort. For projects with heavy user interfacing, such as user application programs or instrument interface applications, such involvement is helpful. Starting at the center, each turn around the spiral goes through several task regions. ?Determine the objectives, alternatives, and constraints on the new iteration. ?Evaluate alternatives and identify and resolve risk issues. ?Develop and verify the product for this iteration. ?Plan the next iteration.Note that the requirements activity takes place in multiple sections and in multiple iterations, just as planning and risk analysis occur in multiple places. Final design, implementation, integration, and test occur in iteration 4. The spiral can be repeated multiple times for multiple builds. Using this method of development, some functionality can be delivered to the user faster than the waterfall method. The spiral method also helps manage risk and uncertainty by allowing multiple decision points and by explicitly admitting that all of anything cannot be known before the subsequent activity starts.WATERFALLS CYCLE The waterfall model is a sequential design process, often used in software development processes, in which progress is seen as flowing steadily downwards (like a waterfall) through the phases of Conception, Initiation, Analysis, Design, Construction, Testing,Production/Implementation and Maintenance. The unmodified waterfall model. Progress flows from the top to the bottom, like a waterfall. The waterfall development model originates in the manufacturing andconstruction industries: highly structured physical environments in which after-the-fact changes are prohibitively costly, if not impossible.Since no formal software development methodologies existed at the time, this hardware-oriented model was simply adapted for software development. The first known presentation describing use of similar phases in software engineering was held by Herbert D. Benington at Symposium on advanced programming methods for digital computers on 29 June 1956. This presentation was about the development of software for SAGE. In 1983 the paper was republished with a foreword by Benington pointing out that the process was not in fact performed in strict top-down, but depended on a prototype.The first formal description of the waterfall model is often cited as a 1970 article by Winston W. Royce, though Royce did not use the term waterfall in this article. Royce presented this model as an example of a flawed, non-working model (Royce 1970). This, in fact, is how the term is generally used in writing about software development—to describe a critical view of a commonly used software practice. In Royces original waterfall model, the following phases are followed in order: 1. Requirements specification 2. Design 3. Construction (AKA implementation or coding) 4. Integration 5. Testing and debugging (AKA Validation) 6. Installation 7. Maintenance SDLC Systems Development Life Cycle (SDLC) is a process used by a systems analyst to develop an information system, including requirements,validation, training, and user (stakeholder) ownership. Any SDLC should result in a high quality system that meets or exceeds customer expectations, reaches completion within time and cost estimates, works effectively and efficiently in the current and planned Information Technology infrastructure, and is inexpensive to maintain and cost-effective to enhance.Computer systems are complex and often (especially with the recent rise of Service-Oriented Architecture) link multiple traditional systems potentially supplied by different software vendors. To manage this level of complexity, a number of SDLC models or methodologies have been created, such as waterfall; spiral; Agile software development; rapid prototyping; incremental; and synchronize and stabilize. SDLC models can be described along a spectrum of agile to iterative to sequential. Agile methodologies, such as XP and Scrum, focus on lightweight processes which allow for rapid changes along the development cycle.