SOFTWARE DEVELOPMENT CYCLE
•Software Development Life Cycle (SDLC) is a process used by the software industry to design, develop and test high-quality software.
•The SDLC aims to produce high-quality software that meets or exceeds customer expectations, reaches completion within times and cost estimates.
•SDLC is the acronym of Software Development Life Cycle.
•ISO/IEC 12207 is an international standard for software life-cycle processes. It aims to be the standard that defines all the tasks required for developing and maintaining software
A typical Software Development Life Cycle consists of the following stages −
Stage 1: Planning and Requirement Analysis
•Requirement analysis is the most important and fundamental stage in SDLC. It is performed by the senior members of the team with inputs from the customer, the sales department, market surveys and domain experts in the industry. This information is then used to plan the basic project approach and to conduct a product feasibility study in the economic, operational and technical areas.
•Planning for the quality assurance requirements and identification of the risks associated with the project is also done in the planning stage. The outcome of the technical feasibility study is to define the various technical approaches that can be followed to implement the project successfully with minimum risks.
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Stage 2: Defining Requirements
•Once the requirement analysis is done the next step is to clearly define and document the product requirements and get them approved from the customer or the market analysts. This is done through an SRS (Software Requirement Specification) document which consists of all the product requirements to be designed and developed during the project life cycle.
Stage 3: Designing the Product Architecture
•SRS is the reference for product architects to come out with the best architecture for the product to be developed. Based on the requirements specified in SRS, usually, more than one design approach for the product architecture is proposed and documented in a DDS - Design Document Specification.
•Developers must follow the coding guidelines defined by their organization and programming tools like compilers, interpreters, debuggers, etc. are used to generate the code. Different high-level programming languages such as C, C++, Pascal, Java and PHP are used for coding. The programming language is chosen with respect to the type of software being developed.
Stage 4: Building or Developing the Product
•In this stage of SDLC the actual development starts and the product is built. The programming code is generated as per DDS during this stage. If the design is performed in a detailed and organized manner, code generation can be accomplished without much hassle
•Developers must follow the coding guidelines defined by their organization and programming tools like compilers, interpreters, debuggers, etc. are used to generate the code. Different high level programming languages such as C, C++, Pascal, Java and PHP are used for coding. The programming language is chosen with respect to the type of software being developed.
Stage 5: Testing the Product
•This stage is usually a subset of all the stages as in the modern SDLC models, the testing activities are mostly involved in all the stages of SDLC. However, this stage refers to the testing only stage of the product where product defects are reported, tracked, fixed and retested, until the product reaches the quality standards defined in the SRS.
Stage 6: Deployment in the Market and Maintenance
•Once the product is tested and ready to be deployed it is released formally in the appropriate market. Sometimes product deployment happens in stages as per the business strategy of that organization. The product may first be released in a limited segment and tested in the real business environment (UAT- User acceptance testing).
•Then based on the feedback, the product may be released as it is or with suggested enhancements in the targeting market segment. After the product is released in the market, its maintenance is done for the existing customer base.
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SDLC Models
•There are various software development life cycle models defined and designed which are followed during the software development process
ØWaterfall Model
ØIterative Model
ØSpiral Model
ØV-Model
ØBig Bang Model
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Waterfall Model
•first Process Model to be introduced
•the linear-sequential life cycle model
•In a waterfall model, each phase must be completed before the next phase can begin
•There is no overlapping in the phases.
•In this Waterfall model, typically, the outcome of one phase acts as the input for the next phase sequentially
•Requirement Gathering and analysis − All possible requirements of the system to be developed are captured in this phase and documented in a requirement specification document
•System Design − The requirement specifications from first phase are studied in this phase and the system design is prepared. This system design helps in specifying hardware and system requirements and helps in defining the overall system architecture.
•Implementation − With inputs from the system design, the system is first developed in small programs called units, which are integrated in the next phase. Each unit is developed and tested for its functionality, which is referred to as Unit Testing
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Waterfall Model - Application
•Some situations where the use of the Waterfall model is most appropriate are −
ØRequirements are very well documented, clear and fixed.
ØProduct definition is stable.
ØTechnology is understood and is not dynamic.
ØThere are no ambiguous requirements.
ØAmple resources with required expertise are available to support the product.
ØThe project is short.
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Waterfall Model - Advantages
ØSimple and easy to understand and use
ØEasy to manage due to the rigidity of the model. Each phase has specific deliverables and a review process.
ØPhases are processed and completed one at a time.
ØWorks well for smaller projects where requirements are very well understood.
ØClearly defined stages.
ØWell understood milestones.
ØEasy to arrange tasks.
ØProcess and results are well documented
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Waterfall Model - Disadvantages
•No working software is produced until late during the life cycle.
•High amounts of risk and uncertainty.
•Not a good model for complex and object-oriented projects.
•Poor model for long and ongoing projects.
•Not suitable for the projects where requirements are at a moderate to high risk of changing. So, risk and uncertainty is high with this process model.
•It is difficult to measure progress within stages.
•Adjusting scope during the life cycle can end a project.
•Integration is done as a "big-bang. at the very end, which doesn't allow identifying any technological or business bottleneck or challenges early.
