What is SDLC? Phases and Models

Software Development Life Cycle (or SDLC in short) is the representation of the life cycle of a software. It is a structured process that ensures the production of high-quality software with minimum possible production time. SDLC outlines the basic plan with different stages, which the developers should follow in order to build the software that meets the customer’s expectations. The plan explains how to build and maintain specific software. Every phase of the SDLC has its own process and deliverables that feed into the next phase. SDLC is sometimes also referred to as “System Development Life Cycle”.

What is the need for SDLC?

Before starting the development of software, the development team must determine a suitable life cycle model. Without it, the development of software would not be in a systematic manner. There must be a clear picture about when and what to do.

Here are the main reasons why SDLC is so important for developing software-

  • It offers a standardized framework that defines the activities and deliverables.
  • It increases the speed of development.
  • It aids in project planning and scheduling.
  • It makes project tracking easier.
  • It decreases project management expenses and the overall cost of production.
  • It decreases project risks.
  • It increases the visibility of all aspects of the life cycle to all stakeholders involved in the development process.

The Software Development Life Cycle consists of the following phases

1. Planning and requirement analysis: It is the fundamental and most important stage in SDLC. It is performed by the senior developers and team members by taking various inputs from the customers. These inputs then are used to plan the approach that should be taken.

2. Defining Requirements: Once the planning is done, the next step is the documentation. This is done by a Software Requirement Specification document which consists of all the product requirements to be designed and developed. There are mainly five types of feasibility checks –

  • Economic: Can the project be completed within the budget or not?
  • Legal – Can this project be handled according to the cyber laws and other regulatory compliances?
  • Schedule – Will the project be completed within the given time schedule or not?
  • Technical – Check whether the currently available computer systems can support the software or not?
  • Operational – Can the exact operations be created that the client requires?

3. Designing the architecture: Based on the requirements specified in SRS, multiple designs approach for the product are proposed in a Design Document Specification. The DDS is reviewed by all the stakeholders and the best design approach is then selected based on various parameters such as risk assessment, product robustness, design modularity, and budget and time constraints.

4. Building the product: This is the phase where the actual development of the software starts. The developers write code as per the DDS. If all of the previous phases were carried out successfully, writing the code would be much easier. Though, there are hundreds of different programming languages such as C, C++, PHP, Python, a specific programming language is used to write the code. The language is chosen based on the type of software being built. For example, if the software is web-based software, PHP can be used as it is a server-side programming language.

5. Testing the Software: Before delivering the software to the customer, thorough testing is performed by a team of software testers. This is done to find out the defects in the software. The defects are reported are fixed. During this phase, the Quality analysis and the testing team may find some defects (termed as ‘bugs’ in the software industry) which they report to the software developers. The development team fixes the bugs and sends them back to quality analysis for re-test. This process is then repeated until the stable and bug-free and the quality standard is reached.

6. Installation/Deployment: Once the testing is done and the software is certified, it is then deployed or installed. Then after this, its maintenance starts.

7. Maintenance: Once the software is installed and the client starts using it, real issues come up and requirements are to be solved from time to time.

Different models of SDLC

Here are some of the most important models of software development Life Cycle:

Waterfall model: This is the widely accepted SDLC model. In this model, the whole process is divided into various phases such that the outcome of one phase acts as the input for the next phase. This is a documentation-oriented model with earlier phases that contains documentation of what to be done in the subsequent phases.

V-Model: In this model, the phases are planned in parallel. So, the development phases are on one side and the testing phases are on the other.

Agile Model: It is a practice in which continue interaction of development and testing is carried out during the SDLC of a project. In this process, the whole project is divided into small incremental builds. All of these builds are provided in iterations.

Spiral Model: This is a risk-driven process model. The development team evaluates the project and determines which elements of the other process models to incorporate.

Iterative: In this process, each development cycle produces an incomplete but deployable version of the software. The first iteration implements a small set of the software requirements, and each subsequent version adds more requirements. The last iteration contains the complete requirement set.