SOFTWARE DEVELOPMENT LIFE CYCLE MODEL

SOFTWARE DEVELOPMENT LIFE CYCLE MODEL

1. Implementation

   • In the implementation phase, the results of the design phase are translated into program code
     • Software that does not meet the needs of the company is wasteful

2. Requirements

   • During the requirements-gathering phase, the needs of the company are outlined
   • Managers and users (and in some cases, clients) make their “wish-lists” about what they would like the software to do. Analysts ask questions about the intended use of the software
   • Analysts ask questions about the intended use of the software, what type of data will be processed, how the software should handle the data, and how the data can be accessed once in the system

3. Testing

   • In the testing phase, the results of the implementation phase are run through a series of tests to verify that it functions and that it meets goals of the requirements phase
     • A testing plan is created to describe the unit tests and system tests that will be performed

4. definition

   • The term software development life cycle model is a way of describing the planning, designing, coding, and testing of a software system, as well as the method in which these steps are implemented

5. Design

   • Focus shifts from the system's results to the way in which those results will be achieved and how the ideas of the requirements-gathering phase are accomplished
     • In the design phase, the results of the requirements-gathering phase are translated into a software design plan.

6. WATERFALL LIFE CYCLE MODEL

   • The Waterfall life cycle model, also known as the classic or linear-sequential life cycle model, is one of the simplest to understand and use.
     • The Waterfall model is characterized by a series of steps that must be completed in a linear, sequential order
   • Waterfall life cycle model
     • Following each phase is a formal review process that results in the decision to proceed to the next phase. Testing is performed late in the development process, and phases do not overlap. When one phase is completed, the entire development effort shifts to the next phase
     • Advantages
       • As a formalized approach to software development, the Waterfall model is simple and easy to use. This model can be easy to implement and manage because each phase has a specific purpose, and development occurs in only one phase at a time. The Waterfall model is appropriate for small development projects in which the requirements are well understood
     • Disadvantages
       • Although the Waterfall model provides a good introduction to software life cycle models, its usefulness is limited. Due to the rigidity of the model, all requirements must be stated explicitly before development begins. If requirements change or are added, the project must start over from the beginning. No working software is developed until very late in the process, and this delay creates a great deal of uncertainty and risk. If errors are made in requirements-gathering or design, they may not be discovered until very late in the implementation or testing phases
   • INCREMENTAL LIFE CYCLE MODEL
     • 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
     • Advantages
       • 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
     • Disadvantages
       • 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

7. V- SHAPED LIFE CYCLE MODEL

   • 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
   • Advantages
     • 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
     • 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 LIFE CYCLE MODEL
     • 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
       • The Spiral model is represented by a spiral passing through four quadrants, which represent the four phases of development. Requirements gathering is performed in the planning phase
     • Advantages
       • The focus on risk avoidance makes the Spiral model ideal for large-scale and missioncritical 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
       • 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
     • SUMMARY
       • All software development life cycle models share common phases of development: gathering of requirements, designing of the software system, coding of software, and the testing of the system. The Waterfall life cycle model is one of the simplest and easiest to use; it consists of five discrete phases that are executed sequentially. The V-Shaped life cycle model adds an emphasis on testing to the Waterfall model. The Incremental life cycle model applies a series of iterations to the Waterfall model. The Spiral life cycle model builds upon the Waterfall and Incremental models and focuses on risk analysis.

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