The software development life cycle: an in-depth study

What is the software development life cycle – and why is it important?

According to Amazon, the software development life cycle (SDLC) refers to ‘the cost-effective and time-efficient process that development teams use to design and build high-quality software.’ At its core, the SDLC ensures greater efficiency, regularity, and consistency is embedded in software development projects.

SDLC uses forward planning to minimise risks to a given project, laying out a roadmap that promotes getting software development right the first time around. It aims to ensure that software meets and exceeds customer expectations – both during production and further down the line. Identifying errors early on in the software creation process enables developers to address them before the project enters successive stages – and before they prove more expensive and complicated to fix.

What are the main phases of the SDLC process?

As a process, the SDLC contains a series of steps – or phases – that differentiate various tasks and allow teams to assign, complete, and measure them.

There are seven distinct SDLC phases:

1. Planning phase/Feasibility phase – In the project planning phase, developers must define the problem, the scope of existing systems, and the objectives for any new features or systems. As well as securing funding and resources, it’s important to outline the project schedule, align it to the development cycle, and identify any potential problems or ‘blockers’ via a risk assessment.
2. Analysis phase – This next phase focuses on requirement gathering and requirement analysis, including prototype system requirements, alternatives to existing prototypes, and the overall needs of end-users. A software requirement specification (SRS) document is often created, which is a detailed plan of all software, hardware, and network requirements and dependencies.
3. Design phase – The software design stage is fundamental to the actual development stage. Team members will outline key aspects such as system interfaces, user interfaces, databases, networks and network requirements. As part of this, the SRS document often evolves into a logical structure that can later be implemented using programming language, and a design document (for reference) is drawn up.
4. Building/Development phase – This building phase of the SDLC centres on writing the code and building the software in line with the design documents and specifications discussed in previous phases. Developers will decide which programming language is more appropriate – for example, PHP or C++ — and follow any organisational coding guidelines.
5. Testing phase – Software testing is a critical part of the SDLC process to ensure that there are no bugs or defects in the source code or system, that the software meets quality standards, project requirements and other metrics, and that the desired user experience has been achieved. Here are 10 best practices for software testing that can help to ensure that your testing is robust. This phase might include code review (to ensure code quality), security testing, unit testing, acceptance testing, penetration testing, adaptability testing, integration testing, and DevSecOps (short for ‘Development, Security and Operations’, which can also take place at any point throughout the SDLC).
6. Deployment phase – Once the final product and the intended deliverables are finalised and ‘ready for market’, the software can be deployed from the test/production environment into the ‘live’ environment. This phase is also known as the Implementation and Integration phase.
7. Maintenance phase – Once a product is in the hands of end-users, the SDLC is still not complete. In fact, many require continuous integration in order to maintain quality standards, launch new features, and evolve over time to keep up with end-user needs. Development teams must now concentrate on implementing any post-deployment changes, handling issues raised by user reports, and dealing with residual bugs that were not addressed before deployment.

The overall software development and project management timeline will vary according to the size and complexity of the project and software applications.

What are the different SDLC models?

There are many different approaches to the development cycle, and selecting the right model for your project’s needs will depend on the type of project, the stakeholders, the measures of success and intended outcome, and the resources and skills available.

Here are some of the most commonly used models in the software development process:

• Waterfall model – The Waterfall methodology is logical, straightforward, easy to manage, and simple to understand: it focuses on completing a phase before progressing to the next. An individual stage relies on information gathered from the previous stage, and each has its own project plan. However, its inflexible structure can lead to delays that impact overall timelines, little room for revisions, and issues that persist until the maintenance phase. This can be particularly problematic with ongoing and long-term projects.
• Iterative model – As its names suggest, the Iterative approach is built on repetition. From the outset, a set of software requirements are implemented, before undergoing testing and evaluation to identify further requirements. New versions of the software are produced with each iteration, and the process is repeated until the finished product is complete. As this model is based on creating a working version of the software from the beginning, changes further down the line are usually less expensive. However, the inherent repetition this model requires can burn through available resources.
• Agile model – Emerging in the early 2000s, Agile methodologies are characterised by ‘fast failure’ and continuous release cycles that build on small, incremental changes from the previous release. By testing the product at each iteration, teams are able to identify minor issues and vulnerabilities before they evolve into major issues and keep stakeholders up to date with progress. The Agile methodology is often used in conjunction with the ‘Scrum’ framework, helping teams to structure, manage and monitor the progress of more complex development projects (which are broken down into ‘sprints’).
• Lean model – The seven Lean principles of SDLC – inspired by the ‘lean manufacturing’ process – are: eliminate waste, amplify learning, decide as late as possible, deliver as fast as possible, empower the team, build in integrity, and optimise the whole. In practice, this might look like reducing the amount of documentation, eliminating unnecessary meetings, and avoiding multitasking. The Lean process promotes only working on what needs to be worked on at any given time, with the ultimate aim of creating value for end-users and increasing satisfaction.
• DevOps model – This model relies on close collaboration between Developers (‘Devs’) and Operations (‘Ops’) teams to speed up innovation and deployment. DevOps is chracterised by continuous feedback, frequent but small updates, automation, and overall process improvement. It aims to create more reliable, higher quality software products and functionalities.
• Spiral model – Spiral methodologies are incredibly flexible and well-suited to large projects involving highly customised products. It continually passes through four phases – in a figurative ‘spiral’ – until the project is complete: planning, risk analysis, engineering, and evaluation. The risk analysis/risk management element of the Spiral model is particularly beneficial as it enables teams to identify potential issues ahead of time and work to mitigate them.

Other SDLC models include the Big Bang model, the RAD model, the Prototyping model, and the V-model (an extension of the Waterfall model).

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