Software life cycle models
- 2. CONTENT: WHAT IS SOFTWARE LIFE CYCLE MODELS? THE WATERFALL MODEL. THE RAPID APPLICATION DEVELOPMENT(RAD) MODEL. PROTOTYPING MODEL. SPIRAL MODEL.
- 3. SOFTWARE LIFE CYCLE MODELS
- 4. What is software life cycle models ? A framework that describes the activities performed at each stage of a software development project. The software life cycle typically includes a requirement phase, design phase, implementation phase, test phase, installation and Check out phase, operation and maintenance phase and sometimes retirement phase. A software life cycle model is a particular abstraction that represents a software life cycle and sometimes is often a called a software development life cycle (SDLC). Software life cycle models describe various phases of the software cycle and the order in which those phases are executed. There are tons of models, and many companies adopt their own, but all have very similar patterns.
- 5. Some of the models as follows. The Water Fall Model. The Rapid Application Development (RAD) Model. Prototyping Model. Spiral Model.
- 6. Waterfall model Requirement and Specification Operation & Maintenance Design Implementation & Unit testing Integration & System testing
- 7. Waterfall model Waterfall approach was first SDLC model to be used widely in software Engineering to ensure Success of the Project. In “The Waterfall” approach, the whole process of software development is divided into separate phases. The phases always occur in this order and do not overlap and the developer must complete each phase before the next phase begins. This model is named “Waterfall Model”, because its diagrammatic representation resembles a cascade of Waterfalls.
- 8. PHASES: 1.Requirement and Specification: The goal of this phase is to understand the exact requirements of the customer and to document them properly. This activity is usually executed with the customer, The requirements describe the “what” of a system , not the “how”. 2.Design and Specification: The goal of this phase is to transform the requirement specification into a structure that is suitable for implementation in some programming language. This work is documented and known as software design description(SDD). 3.Implementation : In this phase design is implemented. If the SDD is complete, the implementation or coding phase proceeds smoothly, Because all the information needed by the software developers is contained in the SDD. 4.Integration & System testing: This is very important phase, because after the implementation of software, developer will test all the facts in software and purpose of unit testing is to determine that each independent module is correctly implemented. 5.Operation & maintenance: Software maintenance is a task that every development group has to face, Working software is not available until relatively late in the process, thus delaying the discovery of serious errors. It is also does not incorporate any kind of risk assessment.
- 9. Advantages: Simple and easy to use. Easy to manage due to the rigidity of the model-each phase has specific deliverables and a review process. Phases are processed and completed one at a time. Work well for smaller projects where requirements are very well stable. Disadvantages: It is difficult to respond to changing customer requirements. Adjusting scope during the life cycle can kill a project. High amounts of risk and uncertainty.. Poor model for long term projects.
- 10. Rapid action development (RAD) Model.
- 11. RAD model is similar to Waterfall model , In RAD, Model development should be done in specified time. RAD model is suitable for the small project where all the requirements are gathered before starting development of the project and no any concrete plan required. Developers moves faster in RAD model with minimum errors RAD model follows the incremental delivery of the modules. The main goal of RAD model is to make the reusability of the developer components. In this model, quick initial views about the product are possible due to delivery of rapid prototype. Rapid action development (RAD) Model.
- 12. PHASES: There are four phases in this model. Requirements planning: In this phase we are captured the requirements and established the workshop utilized structured discussion of business problems. Only issue is the active involvement of users for understanding the project. User description: In this phase joint the team of developers and understand & review the requirements. And the team may use automated tools to capture information from the users. Construction phase: This phase combines the detailed design , coding and testing phase of waterfall model, then we release the product to customer.( “DO UNTILL DONE”) Cut over phase: This phase incorporates acceptance testing by the users, installation of the system, and user training.
- 13. Advantages: High skilled resources required. On each developer phase client’s feedback required. Automated code generation is very costly. Difficult to manage. Not a good process for long and big term project. Fast application and delivery. Least resources and testing are required. Very flexible if any changes are required. Cost effective. Good for small projects. Disadvantages:
- 15. PROTOTYPING MODEL: In this model, a prototype (an early approximation of a final system or product) is built, tested, and then reworked as necessary until an acceptable prototype is finally achieved from which the complete system or product can now be developed. The prototype may be a usable program,but it is not suitable as the final software product. The developers should develop prototype as early as possible to speed up the software development process. After the finalization of software requirement and specification document, the prototype is discared and actual system is then developed using the waterfall approach. Prototyping is an attractive idea for complicated and large systems for which there is no manual process or existing system to help determining the requirements.
- 16. Advantages: Users are actively involved in the development Errors can be detected much earlier. Quicker user feedback is available leading to better solutions. Missing functionality can be identified easily. Confusing or difficult functions can be identified. Disadvantages: Leads to implementing and then repairing way of building systems. Practically, this methodology may increase the complexity of the system as scope of the system may expand beyond original plans. Incomplete application may cause application not to be used as the full system was designed Incomplete or inadequate problem analysis.
- 17. When to use Prototype model: Prototype model should be used when the desired system needs to have a lot of interaction with the end users. Typically, online systems, web interfaces have a very high amount of interaction with end users, are best suited for Prototype model. It might take a while for a system to be built that allows ease of use and needs minimal training for the end user. Prototyping ensures that the end users constantly work with the system and provide a feedback which is incorporated in the prototype to result in a useable system. They are excellent for designing good human computer interface systems.
- 18. Spiral MODEL:
- 19. Spiral MODEL: The spiral model is a risk-driven process model generator for software projects. Based on the unique risk patterns of a given project, the spiral model guides a team to adopt elements of one or more process models, such as incremental, waterfall, or evolutionary prototyping. Planning Phase: Requirements are gathered during the planning phase. Requirements like ‘BRS’ that is ‘Bussiness Requirement Specifications’ and ‘SRS’ that is ‘System Requirement specifications’. Risk Analysis: In the risk analysis phase, a process is undertaken to identify risk and alternate solutions. A prototype is produced at the end of the risk analysis phase. If any risk is found during the risk analysis then alternate solutions are suggested and implemented. Evaluation phase: This phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral.
- 20. Advantages: High amount of risk analysis. Risks are explicitly assessed and resolved throughout the process Focus on early error detection and design flaws. Good for large and mission-critical projects. Software is produced early in the software life cycle. DISADvantages: Time spent for evaluating risks too large for small or low- risk projects. Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive. The model is complex. Risk assessment expertise is required. Developers must be reassigned during non-development phase activities.
- 21. When creation of a prototype is appropriate. When costs and risk evaluation is important. For medium to high-risk projects. Long-term project commitment unwise because of potential changes to economic priorities. Users are unsure of their needs. Requirements are complex. Significant changes are expected (research and exploration). When to use SpiralModel:
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