software development life cycle

software development life cycle

1. software development life cycle models

   • waterfall
     • The Waterfall model is characterized by a series of steps that must be completed in a linear, sequential order.
       • Disadvantages of the Waterfall model
         • Due to these issues, the Waterfall model is inappropriate for complex projects. It should not be used for developing object-oriented software, for long-term or ongoing projects, or for projects in which requirements are unknown or subject to change.
       • Advantages of the Waterfall model
         • The Waterfall model is appropriate for small development projects in which the requirements are well understood.
   • V-shaped
     • Like the Waterfall model, the V-Shaped life cycle model provides a sequential path of discrete phases that must each be completed before development proceeds to the next phase. The phase test plans are developed during each level of development, and once coding is completed, the tests are conducted. Figure 4-3 is a simplified illustration of the V-Shaped life cycle model.
       • Advantages of the V-Shaped model
         • Like the Waterfall model, the V-Shaped model is relatively simple and easy to use. Specific goals are defined for each phase. The focus on preparing test plans early in the process gives the V-Shaped model a higher chance for success. Like the Waterfall model, the V-Shaped model is appropriate for small development projects in which requirements are well understood
       • Disadvantages of the V-Shaped model
         • The rigidity of the V-Shaped model makes it inappropriate for most projects. Like the Waterfall model, all requirements must be stated at the beginning of the project, making it difficult to add or change requirements later in the development process
   • spiral
     • The Spiral life cycle model is similar to the Incremental model but incorporates risk analysis. It is divided into four phases: planning, risk analysis, engineering, and evaluation.
       • Advantages of the Spiral model
         • The focus on risk avoidance makes the Spiral model ideal for large-scale and mission- critical products. At its core, the Spiral model is built on earlier software development models, and it borrows from both the Waterfall and Incremental models.
       • Disadvantages of the Spiral model
         • The Spiral model can cost considerably more to implement than other life cycle models. The risk analysis phase requires highly specific expertise, and the project's success depends on the output of this phase.
   • incremental
     • The Incremental life cycle model builds an iterative approach into the Waterfall model. Development projects are divided into several smaller, more manageable iterations. Each iteration passes through a mini-Waterfall process. Requirement, design, implementation and testing phases are completed for each iteration. Figure 4-4 illustrates the Incremental life cycle model.
       • Advantages of the Incremental model
         • Like the Waterfall model, the Incremental model exhibits some rigidity in that phases cannot be overlapped. Because requirements-gathering and design are performed during each iteration and not before development begins, projects developed using the Incremental model may incur errors in early iterations.
       • Disadvantages of the Incremental model
         • Unlike the Waterfall and V-Shaped models, the Incremental model generates a working prototype early in the development process. The iterative nature of the Incremental model makes it more flexible when adding or changing requirements

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