What is Software Development Lifecycle (SDLC)?
Software Development Life Cycle (SDLC) is a structured process used to design, develop, and test high-quality software. It provides a clear, step-by-step methodology that guides teams through every phase of software creation, from initial planning to final deployment and maintenance.
In software engineering, SDLC models define the sequence of activities involved in building software and provide a standardized roadmap to ensure each stage is executed efficiently and systematically.
Key Takeaways
- SDLC brings discipline and predictability to software development, helping teams manage complexity through clearly defined phases and structured workflows.
- Choosing the right SDLC model directly influences project success, as each model offers distinct advantages in handling requirements, risks, timelines, and change management.
- Integrating security across the SDLC, rather than limiting it to final testing significantly reduces vulnerabilities and supports the shift toward continuous, shared-security practices through DevSecOps.
What is the Importance of SDLC?
The Software Development Life Cycle (SDLC) creates discipline and consistency throughout development. It helps teams minimise risks, avoid ad-hoc decisions, and maintain control over quality as the project progresses. SDLC also supports accurate planning, improves communication among stakeholders, and provides checkpoints to identify issues early. By following a defined lifecycle, organisations can manage resources better, reduce rework, and ensure the final software meets its intended purpose.
How Does SDLC Work?
SDLC works through a set of coordinated phases that take software from initial concept to long-term support. Each phase focuses on specific tasks that help teams to maintain the software in an organised manner.
1. Plan
The planning phase defines the project scope, estimates costs, sets timelines, and allocates resources. The team gathers input from stakeholders such as customers, subject matter experts, and managers to prepare a Software Requirements Specification (SRS).
The SRS aligns expectations, outlines goals, and forms the basis for detailed planning. With clear requirements, the team creates a workable schedule and cost estimate to guide development.
2. Design
In the design phase, software engineers translate the gathered requirements into a practical blueprint for development. They decide on the system architecture, evaluate whether to use existing modules, select suitable technologies, and determine the development tools needed.
3. Implementation
The implementation (or development) phase, is where the design is converted into a code. Developers write the application according to approved design specifications, following coding standards and best practices to make the software functional, efficient, secure, and maintainable application.
4. Testing
The testing phase evaluates the software’s performance, functionality, and usability. Different testing methods are used to identify bugs, inconsistencies, and unexpected behaviors, so the software works as intended before release.
5. Deployment
After successful internal testing, the software is released to end users. Deployment may begin with a pilot or beta release to observe real-world usage. Depending on project needs, deployment can occur on-premise or in the cloud.
6. Maintenance
The maintenance phase begins after deployment. It involves fixing bugs, releasing updates, and adding new features as needed. Regular maintenance keeps the software reliable, secure, and aligned with evolving user and business needs.
Common Software Development Life Cycle Models
There are several SDLC models, each offering a different approach to managing the development process. The choice depends on project requirements, and flexibility. Here are some of the most commonly used models:
1. Waterfall Model
A linear, sequential approach in which each phase must be completed before the next begins. It is simple and structured, but offers limited flexibility once development is underway.
2. Agile Model
An iterative and adaptive model that divides the project into short sprints and encourages collaboration, continuous feedback, and responsiveness to changing requirements.
3. Spiral Model
A combination of design and prototyping with a strong focus on risk analysis. It is well-suited for large, complex, or high-risk projects.
4. V-Model (Validation and Verification Model)
An extension of the Waterfall model where each development phase is paired with a corresponding testing phase. It’s highly structured and ideal for projects requiring rigorous quality assurance.
5. Iterative Model
An approach that builds the software through repeated cycles, with each version refined based on feedback from earlier iterations. New features are added incrementally over time.
6. Big Bang Model
A low-structured model with minimal planning, where development begins immediately with the available resources. It is best suited for small projects or prototypes.
7. Incremental Model
A model that delivers the system in small, functional segments. Each increment builds on the previous one, allowing partial implementation and early delivery of working software.
How Does SDLC Address Security?
A frequent challenge in software development is the tendency to address security only during the testing phase, which comes late in the SDLC after most design and implementation activities are completed. At this stage, security checks are often limited to basic scanning and penetration testing, which may not reveal deeper or more complex vulnerabilities.
This challenge can be effectively addressed by adopting a DevOps approach with integrated security, known as DevSecOps. It incorporates security practices across every phase of SDLC, providing continuous protection rather than relying on late-stage fixes. It follows a shared responsibility model, where everyone involved in the developmemnt pipeline contributes to maintaining security throughout the lifecycle.
Key Terms
Software Requirements Specification (SRS)
A document that captures functional and non-functional requirements, serving as the foundation for planning and design.
DevSecOps
A development approach that integrates security practices throughout the SDLC, promoting continuous protection and shared responsibility.
Iteration / Increment
Terms used in models like Agile, Iterative, and Incremental SDLC, referring to repeated development cycles or functional segments that gradually build the final system.