16 Key Software Development Life Cycle Models Explained

The software process includes the development, implementation or coding, testing, and maintenance of the software. When done correctly, the created software could become the most effective and feature-rich in the industry. Software is also divided into several categories, but the most significant parts of every software development lifecycle are software development and software testing.

As there are different categories of software development, having the same model for every software type could not be highly effective. With that in mind, there are various software development life cycle models that should be followed for optimum efficacy for software development.

Each software development life cycle model has a unique approach that supports the final agenda of the software. Some models are easy to implement whereas others may be a bit complicated for the developers. No matter what the type, the goal of every model is to make software development easier and more effective without compromising its quality.

Types of Software Development Life Cycle Models

Below explained are the different types of software development models that are proven to be effective in software development.

Type #1 : Spiral Model -

Managing risk is among the most crucial aspects of every major task. The spiral model focuses on risk assessment and management in the software development lifecycle. As the name suggests, the graphical representation of this model appears to be in the shape of a spiral having several loops. Akin to other development models, this one also comes with several phases where each loop represents a phase.

There is no fixed number of phases for this model as the number varies with every project and the risks associated with it. Each phase is further divided into four parts where each part fulfills an essential function.

Find Objectives: Before creating software, its objective should be clear. The objectives are identified, explained, and analyzed in this part. Moreover, alternate solutions are also determined in case of any unforeseen circumstance.
Determine Risks: This is the phase where the solutions are studied to understand the best outcome. The determined solution will be further analyzed for all the risks and the strategy is created to tackle the risk.
Create the next version: Now that the risks are analyzed and the right strategy is created, the previously decided features are developed for the software. Moreover, these features are tested and verified as well.
Review: This is the part where every action done in the previous phase is reviewed and evaluated. Once everything is done, the work on the next phase begins with planning.

Apart from risk handling, there are numerous other benefits of the spiral model of software development including requirement flexibility, customer satisfaction, and excellent results on large projects. On the other hand, its complexity, expensive pricing, complicated time management, and high reliability in risk analysis are some of the reasons why the spiral model is not preferred in some projects.

Type #2: Waterfall Model -

The waterfall model of software development is among the most basic and easy models. In the initial days when this model was introduced, it was practiced widely due to its ease of use. However, as new models were introduced with better functionalities and practical solutions, the waterfall model was left behind. Even though it is not used directly, several other models are based on this software development model.

The basic methodology of this model is that the software development process will be divided into different phases and the next phase can only begin after finishing the previous one, making it sequential. Requirement analysis, designing, development, testing, deployment, and maintenance are the different phases of this model.

Being a basic model, it is easy to use, every stage is defined clearly, every step is well documented, and is suitable for small projects. On the other hand, there are certain limitations to this model. The first one is that there is very little scope of flexibility for error correction.

If any mistake happens between the phases, there is no way to fix it until the entire process is complete. Moreover, there is no provision to skip, reverse or overlap any stages. Due to these reasons, this model is proven to be expensive and tedious.

Type #3: Validation and Verification Model -

Validation and Verification or V model software development is a linear model that goes downward till coding and begins moving upwards afterward and is derived from the waterfall model. The development model is planned in parallel where one side of the V includes verification whereas the other side is all about validation.

Verification phases in this model include requirement analysis, system design, architecture design, module design, and coding. Every phase in this model has a corresponding testing activity or validation including acceptance testing, system testing, integration testing, and unit testing. The next phase cannot be executed till the previous one is completed.

V model ensures that the software quality remains top-notch through ample testing of modules. Early detection of errors in code, specifications, and architecture can be fixed which ensures that the software remains stable. However, changes in the code can be tedious and hefty.

The model is highly effective when the project requirements are well documented, the team understands the technology, and the duration of the project is short. V model is a highly disciplined model that is uncomplicated to understand and manage. However, there are several drawbacks of this model including high uncertainty, ineffectiveness for long projects, and software becoming functional late in the development.

Type #4: Iterative and Incremental Model -

The Iterative and Incremental model is divided into two parts with their respective names. In the incremental model, the process is segregated into small portions called increments where every portion is created based on the previous version.

This approach ensures that the newer version is better and improved than the previous one. On the other hand, the iterative model makes use of iterations that are activities repeated systematically where a new version is built after every cycle till the desired program is built.

In the majority of cases, both these approaches are used simultaneously to ensure that the created software is effective. The benefits of this software development model include reduction in delivery cost, faster software delivery, flexibility to make changes in the software midway, and the ability to create organized prerequisites.

On the other hand, there are several drawbacks to this model as well. The first one is the actual cost of the program. Even though it may reduce the delivery cost, the overall cost is still on the higher side. In addition to that, it also needs the arrangement of cycles and requires a robust plan to make any alterations to the plan in case of any necessary changes.

Type #5: Rational Unified Process -

Created by the Rational Corporation, this model is also known as the unified process model and is designed through unified modeling language. This model is a blend of the iterative and linear framework which lets you create working and flexible software.

The entire model is divided into five phases; Inception, Elaboration, Construction, Transition, and Production. The first phase is all about organizing prerequisites, understanding the risks, and the scope of the software. In the elaboration stage, a working structure of the program is created that will reduce the risks.

The third phase is more about creating the software by integrating codes and functionalities. The fourth phase is the transition where the software is moved to production and deployment. The production phase is the part where the created software is maintained and updated.

Type #6: Prototype Model -

Every software is created for the end-users which is why understanding their needs should be the creator's responsibility. The prototype software development model is based on the same psychology where the development team will understand the needs of users and create a program based on the information.

The developers create a working prototype of the software and are continually developing and improving with the feedback its users provide. Upon the success of the prototype, the final software is put into production.

One of the best things about this model is that it minimizes the alterations necessary by the development team as they already know what the user wants which ultimately saves a lot of time and effort. However, the downside of this is that it may drastically raise the overall production expenses. Moreover, after the final prototype is pushed forward for development, it will not accept any further changes, making it less rigid in the final steps.

Type #7 : Rapid Application Development Model -

Also known as the RAD model, this one is similar to the prototype model. However, it is more about developing the program rather than just planning. Here, the developers will focus on delivering the project in small bits whereas the larger projects are also divided into small parts. Reusing the tools, code, templates, and processes is the highlight of this SDLC model.

The model is divided into five different phases; Business modeling, data modeling, process modeling, application generation, and testing and turnover.

Business Modeling: The first step is business modeling where the flow of information and distribution on business channels is identified and the product is designed accordingly.
Data Modeling: Once the data is collected through the previous phase, it is processed into data objects relevant to software and business.
Process Modeling: The data process from the data modeling is altered to understand the data flow which will be implemented in the business.
Application generation: Upon collecting the data, the next part is to build the software through automated tools, and create prototypes based on data models.
Testing and Turnover: The last phase in this model is testing and turnover where the prototypes are tested in every part, reducing the overall development time.

The reason why this model is preferred is that it can help in creating the software in a short span. In addition, it is highly effective when the software requirements are known, the risks are less, and the budget is sufficient to use automated tools.

Type #8: Agile Software Development Model -

Probably the most widely used software development model, the Agile model is built on the iterative and incremental model. Being an adaptive model ensures that the software is delivered faster. The faster delivery is done by eradicating unnecessary activities that may consume additional time and adapting the process as per the project. One distinctive factor about this model is that it is not just a model, but a group of development processes that have certain similarities and differences.

Type #9: Scrum

When it comes to the most far-famed Agile model, Scrum is surely the one to win the title. The iterations in this model lie between one four-week sprint where software engineering teams will analyze the last spring, make necessary changes to it and create a robust plan for the next sprint. Once a sprint activity is defined, there is no going back and the changes cannot be made.

There are three different roles in the models. The first is the Scrum master who is responsible for arranging the meetings and eradicating any underlying hindrances in the process. The next is the product owner who creates the product backlog and handles the distribution. The scrum team is the last role that handles the entire work and organizes the tasks to complete the cycle.

Type #10: Extreme Programming (XP) -

Unlike the Scrum model, the Extreme Programming model allows you to make alterations after the launch of iteration. The only condition is that the team should not work with the software. In this model, the iterations are between one to two weeks.

The model makes use of development based on several tests, pair programming, CI, uncomplicated program design, and small releases. This model is highly useful when there is frequent change in customer needs.

Type #11: Kanban -

Kanban is the most unique model in all Agile models as it does not have any pronounced iterations. Even if there are any, they are mostly daily sprints. The entire model uses visualization of the details of the project which helps the developers in focusing on the crucial features during development.

Here, the teams use the Kanban Board tool where sticky notes are utilized to keep the team focused and to highlight any scope of improvement. As there is no major planning, the model can be ineffective for long projects. However, this same feature allows the team to make changes whenever they want.

Type #12: Lean -

The Lean model of software development is all about diminishing waste, optimizing production, and putting extra focus on new deliverables. All the unwanted processes are eradicated in the model to save development time. Moreover, it gives importance to all the essential functions of the software to keep it as feature-rich as possible.

However, decision-making in this model is complex as the customers have to make their requirements clear. The model has seven principles and each one focuses on a special area. Those principles are eradicating waste, faster delivery, amplifying learning, optimizing the system, embracing teamwork, enhancing quality, and deferring commitment.

The entire notion of this model is to optimize the process and resources. Using stream maps which leads to the eradication of waste due to duplicate efforts is also part of this model.

Type #13: Aspect-Oriented Software Development (AOSD) -

The software development process includes several approaches like object-oriented, procedural, and structural programming whose primary motive is to make the software stable and resolve all the underlying issues. Still, there can be a possibility of missing out on some issues.

The Aspect-Oriented Software Development approach is implemented to minimize this situation as much as possible. This model addresses the issues that may be missed by the aforementioned approaches. This model uses systematic identification, representation, separation, and composition to make software development effective and reduce crosscutting concerns.

By ensuring an excellent modularization program design mechanism, AOSD drastically reduces the design, maintenance, and development cost of the software. Furthermore, it addresses the cross-cutting issues which ensure small-sized codes.

Type #14: Test-Driven Development -

In Test-Driven Development model, several test cases are created to understand the outcome of the code. Here, the code is tested rigorously in the test cases and if the test fails, the earlier written code is eradicated and new code is written. Afterward, the entire process is repeated till the test is passed. The reason why such a severe testing process is done is to ensure that the code remains bug-free and simple. New code is only written by the developers when a previous automated test is failed.

Developers write small codes during TDD tests to ensure that they pass the test and prevent code duplication. The TDD process begins with adding a test and moving forward to running all the tests to determine whether there is any failed test or not. In case there is a failure, the required improvements are made to the code to test it again. If everything goes written, the code will pass and the same process will repeat for other parts of the code.

Type #15: Cleanroom Software Engineering -

In the traditional software development approach, quality assurance plays a significant role and is mostly done at the culmination of the process. The traditional method has worked wonders in the past, but it relies on eradicating the bugs and issues in the end. Developed by Dr. Harlan Mills, the Cleanroom Software Engineering method is all about performing quality assurance at every phase of the development process.

The idea here is to prevent bugs from happening by testing in the initial stage rather than removing the bugs at the final stages. In addition, it removes the dependency of the team on expensive testing processes.

In most cases, a box structure modeling approach is used in this model where a box is used which is a container that stores information about the system. Mainly there are three types of boxes; Black, State, and Clear box. The black box identifies the system behavior, the state box identifies the state operations or data, and the clear box classifies the transition function of the state box.

The reason why this approach has become widely popular is that it helps the team in delivering excellent quality software, boosts productivity, diagnoses errors in the initial stage, minimizes development time, and saves a lot of resources.

Which is the Best Software Development Life Cycle (SDLC) Model?

Everyone wants to use the best software model for their program. However, there is not the best model that works for everybody. Rather, the model suits as per the requirements. Certain factors should be analyzed to understand which model will be best for you and your customers.

The first thing that you should determine is the level of flexibility you need in development. The waterfall model is great for applications that need high stability whereas the Agile model is excellent for web applications where continuous changes are required.

In addition to that, you should also keep in mind the end-users of your program before picking a model. For instance, if your end-users include a variety of groups with diverse features, Agile should be your choice. On the other hand, waterfall works great for a controlled group of users.

Conclusion:

It is fair to say that no fixed model fits the needs of every software type. At ThinkSys Inc, rather than trying every model, the experts take the suitable approach by understanding the models and determining whether it will be best for you or not. Undeniably, making the right decision in software development is essential as it will impact not just the developer, but the end-users as well.

With that in mind, the experts at ThinkSys Inc analyze the different features of the aforementioned models and take the right decision for your software.

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