SDLC Models [Full Guide]

The saying of “There is more than one way to crack an egg” is both true and useless when applied to software project management. There usually is one strategy that fits better than the others, given your project objectives, scale, priorities, resources, and so on.

Here’s an exhaustive overview of Software Development Life Cycle phases and models to help you pick the framework that suits you the most.

What is SDLC Model?

Let’s sort out the basics before diving headfirst into the numerous types of SDLC models and Agile methodology in software development life cycle. Below is a brief cheat sheet explaining what is SDLC.

What is SDLC and STLC?

SDLC stands for Software Development Life Cycle – a structured approach to the development workflow with continuous product improvement in mind. SDLC determines a course of action thorough the whole development process by checking goals and expected deliverables against the progression achieved at each stage of creating a product.

With a structured plan, developers understand what they’re supposed to build, project managers have the measures of progress, and the client obtains a way to compare the result with what was requested.

QA specialists follow the Software Testing Life Cycle when designing and executing test cases in the same manner as the IT team goes through SDLC stages. STLC begins with analyzing the requirement, followed by test planning, test case development, environment setup, and test execution.

Is SDLC a methodology? 

While a plethora of SDLC methods and frameworks exist, it would be wrong to call SDLC a methodology per se. It is rather a generalized depiction of the SDLC phases involved in the creation of any software product.

Why is SDLC important?

Understanding the SDLC process is a determinative factor for getting and holding a firm grip on the workflow. SDLC enables knowing the “whys”, the “whats”, and the “hows” a project at any given time. It allows defining entry and exit criteria for each phase, along with clear deliverables. You can pinpoint the priority tasks and redistribute the resources timely to ensure that the result will meet business objectives.

What are the stages of SDLC?

Software development consists of five major successive stages. The stages of software development life cycle are nearly identical, whatever life cycle model may be used. So, what are the 5 stages of SDLC?

Stages of SDLC

Stage 1. Requirement Capture and Analysis

“What exactly are we supposed to build?” At the preliminary phase, the team collaborates with the business client and domain experts to mark out the purpose, goals, risks, and opportunities. This research is meant to pinpoint the client’s needs and create an appropriate project roadmap that will mold the entire workflow.

The stage focuses on collecting and analyzing functional and non-functional requirements. At this point, cost estimation and risk evaluation happen as well.

The outcome is a Software Requirement Specification – a detailed description that captures the features, behavior, quality attributes, constraints, etc.

Stage 2. Designing Project Architecture

“How are we going to achieve what we aim for?” This stage is intended for turning software specs into the Product Design Specification – a description that documents the solution and states the success criteria. Design specs include tools to use, interface, structure, logic, dependancy, performance, etc.

Stage 3. Development and Programming

“Let’s build what we planned!” #3 stage is where the dev team takes the spotlight and proceeds to turn design specs into actual lines of code. The stage involves setting up a database and environment, creating UI, writing and compiling source code.

Besides coding, the developers create and run unit tests to validate the logic of individual software units.

The third stage should result in a functional and testable piece of software.

Stage 4. Testing

“Have we built what we wanted?”The fourth stage is when QAs verify whether the result meets the initial business goals. They check whether an app performs and behaves as expected via functional testing. There are also numerous types of non-functional tests necessary to ensure performance, security, usability, compatibility, etc.

The output of this stage is a functional deployment-ready product.

Stage 5. Deployment

“Let’s start using what we’ve built.” Once all the tests have passed, it’s time for the software to go-live. The output of this step is functioning software that’s accessible for actual users.

Sometimes, they divide the first step into two separate phases: Planning and Requirements Gathering.

We can also distinguish the Operations and Maintenance stage – a post-deployment step that involves further product support, patching, and updates.

Therefore, the answer to “what are the 7 stages of SDLC?” is:

  1. Planning
  2. Requirements
  3. Architecture Design
  4. Development
  5. Testing
  6. Deployment
  7. Maintenance

What are requirements in SDLC?

In a nutshell, requirements are statements that define and describe the expected result. Requirements are created at the early stage of a project’s development life cycle and are checked against thorough the whole software development cycle.

Is SDLC a Waterfall?

Agile and Waterfall SDLC are the two contrast types of software development life cycle. Some, but not all development life cycle models fall under the umbrella of the Waterfall system development methodology, while the others correspond with the Agile SDLC model.

What is the difference between SDLC and Agile?

Basically, requirements are statements that establish and describe the expected result. Requirements are created at the early stage of a project’s development life cycle and are checked against thorough the entire software development cycle.

  • Is SDLC a Waterfall? Agile and Waterfall SDLC are the two contrast types of software development life cycle. Some, but not all development life cycle models fall under the umbrella of the Waterfall system development methodology, while the others correspond with the Agile.
  • What is the difference between SDLC and Agile? Agile is a subcategory of system development life cycle models with an emphasis on continuous and iterative development. Agile SDLC model enables creating a minimum viable product that goes through multiple loops of improvement, instead of delivering it all at once.

There are 12 core concepts behind the Agile:

  1. Early and continuous product delivery.
  2. Adapting to requirement change at any stage of development.
  3. Delivering working software frequently and in the short term.
  4. Collaboration between client and dev team through daily meetings.
  5. Trust, motivation and the resources required to deliver the result are the primary ingredients of success.
  6. Personal communication is the optimum way of keeping the project on track.
  7. Functioning software is the #1 indicator of progress.
  8. The client, the contractor, and the user are equally important parts of project creation.
  9. Striving for design excellence.
  10. Mastering the art of getting the maximum result with the least amount of work.
  11. Self-managing teams stand behind the greatest software products.
  12. Looking for opportunities to improve efficiency as a team and adjusting workflow accordingly.

What are the different types of SDLC methodologies?

1. Waterfall SDLC Model

Waterfall SDLC

Waterfall SDLC Model is the oldest, stage-by-stage SDLC approach with the development process being broken down into a sequence of tasks. Each of the tasks starts one after another, which makes the development process look like water flow.

Waterfall methodology phases correspond with the classic SDLC stages. The project moves to the next phase only after all the current stage tasks have been finished and checked against strictly documented standards.

Pros

  • The Waterfall development cycle is highly structured, which means that everyone understands their duties at any given time. With detailed documentation, it’s also easier to train fresh team members.
  • Easy to manage. Each SDLC stage has transparent and stable schedules, checkpoints, and deliverables.

Cons

  • Initial uncertainty. It is challenging to set up complete business requirements far in advance.
  • The Waterfall model leaves very little room for addressing modifications and adapting to changing requirements.
  • Cost of error. Being highly-structured and regulated, the Waterfall software development process makes it tough to correct a fundamental defect in time.

Use cases

  • Large-scale projects with static and explicit requirements.
  • Safety-critical industries that put reliability above flexibility, e.g., defense, aviation, railway.
  • Hardware development projects where there the new parts of a system should be compatible with the older ones.

2. Iterative SDLC Model

Iterarive SDLC

Iterative SDLC Model breaks the software development process into smaller repetitive cycles.

Unlike the SDLC Waterfall, the iterative development process does not call for a  comprehensive set of specs right from the start. You can kickstart the development with a minimum scope of requirements that progressively gain more details and complexity with each iteration.

Another difference from a cascading model is that iterative development cycle enables paralleled development.

Pros

  • You can adjust the requirements and the technical specs of the project on the fly and at lower costs.
  • Flaw detection. With the iterative method, you get an early working prototype, which helps to minimize the cost of bug fixing.
  • Customer evaluation. Since working software is delivered early, you can gain important insights from the customer and adjust it as needed.

Cons

  • Management complexity. The whole process requires more management efforts compared to the linear model.
  • The Iterative SDLC Model is a resource-consuming system life cycle model. In addition, it requires risk analysis expertise.

Use cases

  • Large-scale projects that allow separating the development process into small standalone chunks.

3. Spiral SDLC Model

Spiral SDLC

Spiral SDLC Model is a hybrid between iterative and sequential SDLC methods with an emphasis on the risk control.

When working by the Spiral model, the team proceeds to the next software life cycle stage with design goals in mind and closes it after getting and implementing customer feedback. Process flow goes through increasingly long iterations, hence the name.

The focal point for this method is choosing the best time for switching from a current phase to the next one.

Pros

  • Risk mitigation. Workflow is separated into smaller bits. If some risk arises, the team can close the current phase earlier to take care of it.
  • You can make adjustments and throw in new features even in the late phase.

Use Cases

  • Spiral model suits for developing a brand new product that needs to accumulate enough user feedback.

4. V-shaped SDLC Model

V-Shaped SDLC

V-shaped SDLC Model is a modification of the classic Waterfall approach in which testing occurs at each development phase.

Like the Waterfall, V-shaped is a strict methodology with a cascading workflow. Business requirements are validated via user acceptance tests. System integration testing is used to validate architecture design. Once the product is developed, it goes through unit tests.

Pros

  • Easy to control. Each phase delivers clear and concrete results, making it easy to control and measure success.
  • Flaw detection. Product verification and testing take place at an early stage.

Cons

  • In case of any adjustment, you must review and update the requirements along with the test documentation.
  • The V-shaped model doesn’t produce an early-stage software prototype.
  • Technical resources. This approach requires more technical resources and high testing expertise.

Use cases of V-shaped SDLC Model

  • Projects where meticulous software testing is essential.
  • Small and medium-sized projects with well-detailed requirements.

5. Agile SDLC Model

Agile SDLC

Agile SDLC Model covers a broad category of SDLC life cycle models distinguished by their flexibility and adaptiveness. There are dozens of Agile software development cycle frameworks, the most trendy being Scrum, Kanban, SAFe, Lean, etc.

  • What is Agile coding? In contrast to the sequential system development life cycle methodology, Agile software development life cycle requires only a rough plan initially. The IT team builds, tests, and releases software in ongoing cycles, each featuring small additions, adjustments, and improvements.
  • What is Agile and Scrum? Scrum falls under the subset of Agile development cycle These are the guiding aspects of the Scrum development process:
  • There are three key players in the Scrum project: product owner, a team, and a Scrum master. The Scrum master orchestrates project workflow and keeps track on progress measurements.
  • Scrum Agile software development process consists of “sprints” – brief, time-boxed stages in which a team works to accomplish a specific set of tasks.
  • Scrum planning tools include a product backlog, a sprint backlog, and the burndown chart to track the remaining amount of work.

How Kanban is different from Scrum? Kanban is an approach to project management that facilitates prioritizing tasks via visual cues. Kanban method typically involves a board that displays the status and progression of each task.

Pros

  • Great flexibility. Agile system development life cycle is welcoming to the improvement of functional requirements at any stage of development.
  • Agile software development phases divide the development process into short iterations with clear deliverables.
  • Fast release. Agile methodology phases enable early software prototype release.
  • Flaw detection. Versatile change process allows minimizing the cost of error.

Cons

  • Product completion time is uncertain. Frequent adjustments and changes may  drag out product deployment significantly.
  • Constant changes and improvements complicate the final cost estimation.
  • New requirements may be contrary to the existing architecture.

Use cases of Agile SDLC Model

  • Competitive subject matter market that calls for a product to change dynamically.

6. Big Bang Model

Big Bang Model

Big Bang Model puts coding above anything else and includes little to no planning. As soon as the team receives the requirements, they move straight to the implementation stage.

Pros

  • Big Bang is a straightforward and easy-to-manage approach.
  • This model provides the developers with great freedom to act on their ideas.

Cons

  • Significant risks and uncertainty.
  • Doesn’t suit well for complex and long-term projects.
  • Can become very pricey if the IT team misunderstands the requirements.

Use cases

  • Small and short-term projects with a few developers on board.
  • Projects with a lack of clarity in business requirements.

7. Rapid Application Development model

Rad Model SDLC

RAD Model (Rapid Application Development model) focuses on developing working prototypes and improving the product according to user feedback.

Rapid application development life cycle puts the experience of actual users above abstract design specifications. Prototypes gradually evolve into the completed software.

Pros

  • Better quality. Early user access helps to define and address critical design and technical flaws.
  • RAD model enables improvement of the prototypes to shape them into the desired product.

Cons

  • Continuous interaction between users and devs consumes time and resources.
  • Lack of attention to the non-functional requirements.

Use cases

  • Projects that have to be released in a span of a few months.
  • Projects that require user involvement all through the development process.

8. Software Prototype Model

Software Prototype SDLC

Software Prototype Model refers to developing working prototypes that showcase the functionality but may not completely display the logic of the resulting software.

Similar to the RAD model, the Prototyping approach helps software engineers and designers gain a better understanding of user requirements and expectations.

Pros

  • User involvement and feedback before the implementation of the solution.
  • The team can detect missing functionality, system, and design flaws at an early stage.

Cons

  • Building prototypes may consume too much time and resources.
  • End-users may confuse a rough prototype with a completed product, thus threatening to reputation loss.

Use cases

  • Products that need to have a high amount of interaction with an end-user, such as web interfaces.
  • Products that rely on a quality human-computer interface.

Conclusion

There is no one-size-fits-all approach to software development – each company is a different animal, especially when we’re talking startups. Hopefully, this article helped to shed light on different software life cycle models and determine your perfect match.

No matter which SDLC model you find feasible for your project, Echo can back your choice with a dedicated team of developers. Contact us today to discuss the optimum strategy for achieving your business needs.

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I've founded Echo based on my three passions: engineering, marketing, and headhunting. As a company CEO, it is always hard for me to make time for writing. However, I like sharing my experience with people around.
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Lou Reverchuk

Entrepreneur, Marketer, Writer

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Qizzer

Oh yeah, this is exactly the guide that I’ve been searching for a long time. I am very grateful to you for this. It helped me a lot to write an awesome technical essay in college.

Connor Keith

Really good that you ended this article with “there is no one-size-fits-all approach to software development.” The problem is that far too many companies take this approach and the result is buggy software and products that have no business being released yet (and perhaps shouldn’t be released at all). I’m not a software developer, but it’s clear there are the creation process is as complex as the software itself. Would it be fair to say you need an expert developer to work with any software company?

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