The Four Major Software Development Lifecycle Models And How They Work

The Four Major Software Development Lifecycle Models And How They Work


What is Software Development Life Cycle?

Software Development Life Cycle (SDLC) is the process used by the software industry to design, develop & test high-quality software. It includes 7 phases they are :


4 Major Software Development Lifecycle Models

  1. Agile Model:

    Agile development methodology is one of the fastest-growing trends in software development today. It is one of the simplest and most effective processes to turn a vision for a business need into software solutions.

    Agile is a term used to describe software development approaches that employ continual planning, learning, development, team collaboration, evolutionary development, and early delivery.

    Related Post: How to Integrate Testlink with Mantis Bug Tracker


    When we need to deliver the product early and have no such precise requirements, clients are always included in agile software development because they do not give us fundamental requirements but sprint-wise requirements.

    So when they assign us any module based on the requirements, we have to divide it by the number of sprints; one sprint takes 2 to 4 weeks to complete. When the particular sprint is completed, after reviewing it, we need to release it to the client.

    It encourages flexible responses to changes when the client wants to perform any changes in a specific sprint so we can perform it flexibly.

    Agile software development emphasizes four core values i.e. four principles:

    1. Individuals and Interactions over processes and tools.
    2. Working software over comprehensive documentation.
    3. Customer collaboration over contract negotiation.
    4. Responding to the changes over following a plan.

    What is Scrum in Agile methodology?

    Scrum is an Agile development method that concentrates on managing tasks within a team-based development environment. There are 6 to 8 members in the scrum, including the scrum master, product owner, and scrum team.


    Process flow of scrum Methodologies:

    • Each iteration (module) of a scrum is known as a sprint.
    • The product backlog is a list where all the details are entered to get the end product.
    • During each sprint, the top user stories of the product backlog are selected and turned into the sprint backlog.
    • The team works on a defined sprint backlog by taking sprint planning meetings.
    • The team checks for the daily work (daily scrum meeting).
    • At the end of this sprint, the team delivers product functionality by taking a sprint review meeting.
    • The Scrum team meets again after the sprint review meeting and documents the “Lesson Learn Document” by taking a sprint retrospective meeting.

    Advantages of the Agile Model:

    1. Communication with clients is on a one-on-one basis.
    2. Provides a very realistic approach to software development
    3. Agile Model in software engineering enables you to draft efficient designs and meet the company’s needs.
    4. Updated versions of functioning software are released every week.
    5. It delivers early partial working solutions.
    6. Changes are acceptable at any time.
    7. You can reduce the overall development time by utilizing this Agile Model.
    8. It allows concurrent development and delivery within an overall planned context.
    9. 9. The final product is developed and available for use within a few weeks.

    Disadvantages of the Agile Model:

    1. There is a higher risk of sustainability, maintainability, and extensibility.
    2. Documentation and design should be given more attention.
    3. Without clear information from the customer, the development team can be misled.
  2. Waterfall Model:

    The waterfall model is also known as the “Liner Sequential Model” as it is executed in a sequential manner & Development process is usually unidirectional and flows steadily downwards.

    The waterfall model’s essential nature is that it has an obvious & fixed requirement, i.e., no more changes will be accepted after baselined of the requirements. After the completion of each phase, the review has been taken, so after taking the review, we cannot go back since there is no backtracking in the waterfall model.


    Sequential phases in the Waterfall model are:

    • Requirement Analysis: In this phase, all possible requirements of the System to be developed are captured in a Requirement Specification Document.
    • During this phase, the requirements specifications from the first phase are studied, and a system design is prepared. This system design helps specify the hardware and the system requirements and helps define the overall system architecture.
    • Implementation: With inputs from the system design, the System is first developed in small programs called units, which are integrated into the next phase. Each unit is developed and tested for its functionality, referred to as Unit Testing.
    • All developed units are integrated and tested in the implementation phase before integration into a system. Post integration, the entire System is tested for faults and failures.
    • Deployment of System: the functional and non-functional testing is done, the Product is deployed in the customer’s environment or released into the market.
    • Maintenance: Some issues come up in the client environment. To fix those issues, patches are released. Also, to enhance the Product, some better versions are released & Maintenance is done to deliver these changes in a customer environment.

    Advantages of the Waterfall Model:-

    1. Simple and easy to understand.
    2. Easy to manage due to the Rigidity of the model. Each phase has its own set of deliverables and a review process.
    3. Phases are processed and completed once at a time.
    4. It works well for smaller projects where requirements can be easily understood.
    5. Clearly defined stages.

    Disadvantages of the Waterfall Model:-

    1. Work software is produced late during the life cycle.
    2. High amounts of risk and uncertainty.
    3. Not a good model for complex projects.
    4. Poor model for long and ongoing projects.
    5. Not suitable for projects where the requirements are at a moderate to high risk of changing. So the risk and uncertainty are high with this process model.
    6. It isn’t easy to measure progress within the stages.
    7. Cannot accommodate changing requirements.

    Read More: Optimize continuous delivery with continuous reliability

  3. V-V (Verification & Validation) Model:

    The V- model is an SDLC model where the execution of processes happens sequentially in a V- shape. It is also called as Verification and Validation model. Each phase of the SDLC model must complete before the next phase starts. The sequential design process is similar to the Waterfall Model. Testing activities are carried out or planned in parallel with related development activities.


    Verification involves a static analysis method (review) done without executing the code. It is the process of evaluating the product development process to find whether specified requirements are met.

    Validation It involves a dynamic analysis method, i.e., functional and non-functional; testing is done by executing code. Validation is the process of classifying the software after the completion of the development process to determine whether the software meets the customer’s expectations and requirements.

    Following are some pointers for the most suitable scenarios to use the V-Model application:

    • Requirements are well-defined & documented, and fixed.
    • Product definition is stable.
    • Technology could be more dynamic and better understood by the project team members.
    • There are no ambiguous or undefined requirements.
    • The project is short.

    Advantages of the V-V Model:

    1. Easy to Understand.
    2. Testing methods like planning and test designing happen well before coding.
    3. This saves a lot of time. So a higher chance of success over the Waterfall model.
    4. It avoids the downward flow of defects.
    5. Works well for small plans where requirements are easily understood.

    Disadvantages of the V-V Model:

    1. Very rigid and least flexible.
    2. Not suitable for a complex project.
    3. If any changes happen midway, then the test documents and the required documents have to be updated.
    4. Not suitable for projects where the requirements are at a moderate to high risk of changing.
    5. Once an application is in the testing phase, it is difficult to go back and change the functionality.
  4. Spiral Model:

    This spiral model combines the Iterative development process model and Sequential Linear development model, i.e., the Waterfall model, with a very high emphasis on Risk analysis. It allows us the Incremental releases of the product or Incremental refinement through each iteration around the spiral. The spiral model has four phases:

    The following illustration is a representation of the spiral model, listing the activities in each phase are as below:


    Objective Identification:

    The objective identification phase starts with gathering the business requirements in the baseline spiral. In the subsequent spirals, as the product matures, Identification of the system requirements, Subsystem requirements, and Unit requirements are all done in this phase. This phase also includes understanding the system requirements by communicating continuously between the Customer and the system analyst. The product is deployed in the Identified market at the end of the spiral.

    Evaluation and Risk Management:

    Risk analysis also includes identifying, estimating, and monitoring risks’ technical feasibility and management, such as schedule Slippage and Cost overrun. After testing the build, at the end of the first iteration, the Customer evaluates the software and provides feedback.


    The design phase starts with the conceptual design in the baseline spiral. It involves Architectural design, Logical design of modules, Physical product design, and the final design in the subsequent spirals.

    Construct or Build:

    The constructed phase refers to producing the actual software product at every spiral. In the baseline spiral, the product is just thought of, and the design is being developed in this phase to get customer feedback.

    Then the subsequent spirals with higher clarity on the requirements and design of a detailed working model of the software called to build are produced with a version number. These builds are sent to the Customer for their feedback.

    The following are some pointers of the most suitable scenarios to use the V-Model application:

    • A Spiral model in software testing is used when the project is significant.
    • The spiral methodology will be used when releases are required to be frequent.
    • When the creation of a prototype is applicable.
    • When the risk and the cost evaluation are important.
    • The spiral methodology is helpful for medium to high-risk projects.
    • When requirements are unclear and complex, the Spiral model is valid.
    • When changes may be required at any time.
    • When the long-term project commitment is not feasible due to the changes in economic priorities.

    Advantages of the Spiral Model:

    1. Development is fast.
    2. More extensive projects/software are created and handled strategically.
    3. Risk evaluation is proper.
    4. Control towards all the phases of development.
    5. More and more features are added systematically.
    6. Software is produced early.
    7. There is always a space for customer feedback.

    Disadvantages of the Spiral Model:

    1. Risk analysis is an important phase, so it requires expert people.
    2. It is not beneficial for a smaller project.
    3. The spiral may go infinitely.
    4. The document is more as it has intermediate phases.
    5. It is costly for smaller projects.