Software Development Lifecycle (SDLC): An Introduction

By Stephen Watts October 12, 2023

The software development lifecycle, or SDLC, is a systematic process for building software. It's composed of several methodical stages that prioritize increasing system efficiencies, proper planning and rigorous testing. This enables organizations to produce the highest quality software in the shortest possible amount of time, all while minimizing costs.

The first phase of the SDLC typically begins by gathering and analyzing the requirements for the development project. Once the project requirements have been clearly defined and planned, the SDLC proceeds to the design phase and development phases, during which the software is architected and built. In the next phase, the software enters the testing phase to ensure it's error free and works as expected before being deployed to users. The final stage of the SDLC is ongoing monitoring and maintenance to discover and resolve any bugs that slipped through the cracks.

The SDLC model isn't a single methodology but rather a framework that encompasses several different software development models. These include:

• Waterfall model: The oldest and most straightforward software development model gets its name from its linear beginning-to-end flow. Each stage follows its own plan and must be completed before the next stage can begin, with one stage waterfalling into the next.
• Iterative process model: Rather than aiming to produce a fully developed application all at once, developers quickly build an initial version of the software, then make improvements with succeeding small iterations. This approach is typically used to develop larger applications, allowing development teams to break the project down into more manageable chunks and deploy software to users more quickly.
• Agile: Based on the iterative approach, the agile model divides the project into multiple cycles and delivers a succession of releases. Each release generates feedback that's incorporated into the next release, allowing organizations to quickly adapt to an ever-changing market, while reducing risks particular to the waterfall model.
• Spiral model: The spiral approach combines elements of the waterfall and iterative models. It repeats the planning, design, build and test stages of development in linear succession, making iterative improvements with each pass through the process.
• V-model: This approach extends the waterfall model by incorporating testing and validation at each stage of development rather than including a standalone testing stage at the end.
• Big bang model: This approach minimizes formal structure and processes, instead relying on large amounts of time, effort and resources to produce software. This makes it the most high-risk of the models and best suited for small teams.

The Spiral Model is one of several software development models, which combine elements of iterative and waterfall models.

The SDLC is an essential aspect in developing high quality software. In this guide, we'll look at the different stages of the SDLC, why it's important, and how it's used by organizations. We'll also explain some best practices that can help you get the most from your SDLC efforts.

Software Development Lifecycle Basics

The purpose of the SDLC process is to provide a framework for controlling the software development process and ensuring all project requirements are met. It lays a foundation for gaining clarity around a software project's goals, planning activities and deliverables, identifying and minimizing risks, vetting software quality, managing customer expectations and maintaining the product once it's deployed.

The structure that SDLC provides offers many advantages, including:

• A clear end goal: Developing modern applications is complex and resource-intensive. Project planning can be easily derailed by poor resource management, scope creep, missed deadlines and other issues. The SDLC maintains focus on the project's goals and potential impediments so that the development process is implemented with precision and runs smoothly from inception to completion.
• Higher quality software: Poor quality software is more than an annoyance for end users. A buggy application can cause service issues when it's integrated with the organization's other systems, resulting in downtime, lost transactions and a diminished reputation, among other things. Thorough testing ensures that software meets its technical and user requirements and is free of defects before it's delivered to users.
• Team member flexibility: The loss of a project team member can delay the project if they must review it from the beginning to get up to speed. An effective SDLC maintains complete and detailed records of the entire project, so anyone joining midstream can pick up where the previous member left off.
• Reduced costs: The SDLC emphasizes clear deadlines and deliverables, while offering a structure that lets you see all a project's timetables and costs. This helps keep the project on budget and enables the project manager to focus more on improving efficiencies and productivity.
• Continuous improvement: SDLC stages are designed to create a feedback loop. Information gathered from the testing, deployment and maintenance stages feeds back to the earlier stages, allowing you to make continuous improvements until you have an optimal product.

The SDLC is critical to developers because it ensures they build the highest-quality software coupled with the lowest possible cost estimates in the shortest possible time. Specifically, it offers developers advantages such as:

• Greater clarity: Modern software projects are large, complex and can quickly become overwhelming. The SDLC provides developers with a detailed plan and clearer vision of the end product and helps them more easily identify tasks, risks and problems at every stage of the process.
• Better quality control: Thorough software testing built into the SDLC helps prevent problems from being released in the live software. Regular checks keep the project moving smoothly so developers can focus on building the software rather than troubleshooting issues.
• Smoother processes: Each stage of the SDLC is designed to flow into the next stage or feed back into the previous one. When developers hit an obstacle, they can follow this loop to determine a way to overcome it.

What are the different stages of the SDLC?

Typically, the stages of the SDLC are:

• Requirements analysis and planning: The SDLC begins with senior team members collecting requirements from the project's stakeholders and determining the feasibility of the project, as well as planning a basic approach. This stage should clarify the scope of the project and any anticipated issues, risks and opportunities.
• Defining requirements stage: Once the requirements have been gathered and analyzed, the next stage is to clearly define them and get them approved by stakeholders, typically through a Software Requirement Specification (SRS) document that includes all project specifications collected during the requirement analysis and planning phase.
• Design stage: After the documented requirements are approved, product architects determine the best and most cost-effective architecture for the product based on the SRS. Typically, more than one design is proposed and documented in a Design Document Specification (DDS), with the most optimal one selected based on timeline, robustness and cost.
• Development stage: The product is built in this stage. Developers generate the programming language code according to the DDS and follow the organization's coding standards and guidelines. Project modules and new features are expected to be completed within the project's established deadlines
• Testing stage: As each component of the software build is completed, it's sent to the testing team where it's thoroughly tested to ensure it's working as expected. Any discovered defects are documented and sent back to the development team for correction.
• Deployment and maintenance stage: Once the first version of the software has been tested and any defects removed in the production environment, it's delivered to a large group of end-users, who will often uncover bugs and errors that weren't detected during the testing stage. Any user feedback will be incorporated into the next release of the software. Software updates, security patches and feature enhancements are also implemented during this stage.

The six stages of the SDLC include planning, defining requirements, design, development, testing and finally deployment.

System Development vs Software Development

The difference between the software development lifecycle and the system development lifecycle is that the former is a framework for software development and the latter is a process for the development of a structured information technology system.

Like the software development lifecycle, the system development lifecycle is a structured project management model that includes several stages, including:

• Planning stage: The system development lifecycle begins by defining the project scope, creating an action plan for the project, and identifying the issues the project would resolve. Teams, timelines, budget, security and other project aspects that are critical for success are defined at this stage.
• Analysis stage: The team analyzes the system's functional requirements to ensure it will meet stakeholders' expectations. The requirements are documented, and a feasibility study is conducted to make sure the organization can meet the project's financial, technological and organizational needs.
• Design stage: During the design stage, the team determines the design of the system's architecture, network, databases, security and user interfaces according to the project's requirements.
• Development stage: The system is built during this stage. Hardware is configured and fine-tuned, and software engineers write the required code.
• Testing and integration stage: All the system modules are brought together and tested for defects and interoperability to ensure the system performs as expected and meets project requirements.
• Implementation and release stage: Once the new system has been thoroughly vetted, it's rolled out into production to replace the old system and is made available to end users.
• Maintenance stage: The new system is monitored to make sure it continues to operate correctly and to uncover any bugs that weren't found during the testing stage. The system continues to undergo frequent maintenance and updates during this stage.

Software Development vs Agile

The SDLC is a framework for successfully developing modern software applications, while Agile is a particular development methodology within that framework.

More specifically, the SDLC defines the different stages, steps and processes for designing and developing software. It's meant to ensure that high-quality software is built efficiently. Multiple models are constructed around the SDLC framework, each with their own steps and processes. Agile is one of these development models.

Conversely, Agile is a popular approach for organizations that want to create a continuous delivery environment. It's centered around iterative development, short development cycles, gathering feedback and adapting to new requirements.

While Agile is considered an SDLC approach to software development, there are some key differences. Agile is generally a faster and less systematic approach than the SDLC. Agile also follows a continuous cycle and allows dynamic changes in requirements, whereas the SDLC is sequential, and requirement changes aren't allowed after the initial stages. Finally, the SDLC relies heavily on the involvement of a project manager, and Agile requires close customer involvement.

SDLC Tools and Best Practices

The SDLC employs many tools to manage the software development process. Some of the most popular include:

• Jira: This was originally designed as an issue-tracking tool for software companies, but as the Agile methodology became widely adopted by organizations, Jira expanded to become a powerful workflow management tool used to track a variety of work items throughout the SDLC.
• Trello: Trello is a popular online project management system used widely in software development, employing the Japanese Kanban methodology to help the team visualize tasks so they don't get overlooked or repeated. Teams can efficiently organize their work using digital cards and columns according to stages of development.
• Git: An open-source distributed version control system for tracking changes in files, developers rely on Git to coordinate work among teams collaborating on a project. Git allows each team member to work on a local clone of the project that's a complete version control repository. Git helps maintain the integrity of source code and allows developers to more easily track changes and contributions to the project.
• Source Tree: Source Tree is a free graphical interface for the Git and Mercurial version control systems, providing a more intuitive way for developers to interact with and manage their repositories, while simplifying their workflow so they can focus on writing code.
• Confluence: Confluence is a team collaboration platform that makes it easier for software teams to organize, share and discuss information about their development projects. It promotes more effective collaboration among teams working on different stages of the SDLC by providing a centralized space for connecting, communicating, sharing content and documenting knowledge

Some SDLC best practices to include:

• Establish requirements before you begin: Gathering and analyzing requirements is the first stage of the SDLC for good reason. It's the most critical determining factor for your project's success as it ensures everyone working on the project has a clear vision of the finished product. Before designing your software, ask what the goals and objectives for the application are. Determine what features and functionalities it will need to meet those goals and objectives. Be specific about when you need the software to go live, and decide on indicators by which you can determine if the project is successful.
• Use automation: Software development projects generally involve many developers working individually on different tasks. Once a particular task is completed, another team member performs their task, and the project moves forward in this way until it's completed. But managing this changing of hands manually eats up time and runs the risk of introducing errors into the software. Automated tools can be used in key stages of the development lifecycle to smooth transitions between team members and speed up processes by completing repetitive low-level tasks.
• Choose the "right" development approach: As mentioned, there are several proven software development methods, including waterfall, Agile and spiral. Rather than adopting the one that is perceived to be the best or most popular, consider which one will best meet your project's unique needs. Waterfall has received plenty of criticism in the modern development era, but it is still a relevant approach for certain projects such as those that have unambiguous and fixed requirements or those of short duration. Effective application and adherence to a particular approach will also be determining factors in the success of your project.
• Test throughout the SDLC: Software problems can arise at any stage of the SDLC, and the deeper you get into a project the harder it will be to resolve them. Waiting to tackle a huge set of revisions in the later stages of a project is a surefire recipe for delayed deployment. Testing software continuously as it's being built will allow you to fix problems as they occur, ensuring the SDLC goes smoothly and your product is delivered on time.
• Share what you learn: Each pass through the SDLC offers opportunities to improve it. Anything learned from a previous project can be used to develop new or more effective strategies for future projects. Be sure to share insights with all stakeholders once a project is completed.

Several emerging trends will impact the SDLC in the coming years. Artificial intelligence (AI) will play a bigger role both in the development process, with AI being used to write code and test software, as well as the software product where it will be used to enhance the user experience. There will likely be a greater exploration of software that can support different platforms with a single code base, eliminating the need for different versions of the same app for iOS and Android, for example. Security will also be a greater focus in software development, with cybersecurity measures increasingly being integrated into application.

The Bottom Line: Successful software development starts with the SDLC

Building modern applications is often a Herculean undertaking. Without clear objectives and processes, your software project runs the risk of getting derailed with no clear way to get back on track. Following the stages and steps of the SDLC ensures from the outset that you can build the software you envision that perfectly meets the needs of your customers.

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