What is the software development lifecycle (SDLC)?
The software development lifecycle (SDLC) is a project management framework that describes the stages and tasks involved in each step of software development. The SDLC model maps the complete software development process from its initial planning through maintenance and eventual retirement and replacement of the completed application.
An important goal of the SDLC is to quickly and efficiently produce high-quality software in a series of phases or steps. The number of steps in the SDLC varies depending on the business and its software product goals. For example, at the most basic level, teams design, develop, test and then release software. Upon release, the software is maintained until it is discontinued. Typically, there are between five and seven steps -- although there can be more.
What are the steps of the SDLC?
In general, the SDLC process follows these phases:
- Evaluate the existing software. If there is existing software in place, then teams identify any deficiencies in the software. Teams can accomplish this by interviewing users and consulting with support personnel, as well as by reviewing metrics gathered through application performance monitoring (APM) tools. This step provides insight into the strengths and weaknesses of the current software and what can be implemented in the next round of development.
- Plan the new software requirements. Deficiencies in the existing software must be addressed. Teams make specific proposals for improvements, such as new features and functionality. If no previous software is in place, this phase simply involves defining the requirements for proposed software. Requirements can include hardware, operating systems (OSes), programming and security.
- Design the proposed software. The design phase turns the software specifications into a design plan. Teams develop plans concerning the architecture, hardware, OSes, programming, communications and security issues.
- Develop the new software. During the development phase, the developers build the code. Developers must obtain and install new components and programs.
- Test the software. The test phase ensures the software works before integration and management. The software should be operating to the original specifications by the end of this stage. The code's structure determines which tests the team uses. Software testing is a large step in the SDLC, so many organizations make testing separate from the development stage, as in this list.
- Push the software to users. Sometimes, new software is phased in according to application or location to gradually replace an old product. In other cases, the old system is shut down, and users move over to the new system all at once.
- Monitor the software. Organizations should exhaustively evaluate software for performance and stability. Organizations use logs, as well as APM and other metrics-gathering tools, for monitoring. Any concerns should be reported to the development team for remediation in patches or ongoing software maintenance efforts.
Other organizations may include steps for deconstructing, retiring and replacing software as well.
What are the different SDLC models?
There are various SDLC models to choose from. The right one depends on the requirements of any given project. Several models can be combined into a hybrid methodology. Documentation is crucial, regardless of the type of SDLC model for a given application, and is usually created in parallel with the development process.
For example, the Waterfall model is a linear, sequential approach to the SDLC that emphasizes a logical progression of steps. Similar to the way water creates a waterfall by flowing down a creek and over a cliff, once development work in a Waterfall model has been completed, it cannot be revisited. The term is often associated with large, monolithic software products developed before the turn of the century. Many developers do not develop code with Waterfall now since it is considered inefficient to finish a piece of code and not revisit it.
In contrast, the Agile model for SDLC is a more modular and flexible approach. Agile approaches software development in incremental cycles, called sprints. Each sprint is iterative, and code is designed to be modular.
Other popular SDLC models include the following:
- Rapid application development. RAD was conceived in response to the downsides of the Waterfall model and focuses on a more adaptive approach to software development.
- Joint application development. JAD includes the end user in the design and development steps through workshops.
- Prototyping model. The prototyping model requires a working prototype to be made before software development is carried out.
- Spiral model. The spiral model combines the Waterfall and prototyping models.
- Synchronize-and-stabilize model. In this model, teams work on individual software models. Teams then bring their code together and debug the code.
- V-model. The V-model maps out a flowchart in the form of a V. Business requirements are created in the downward sloping part, the base of the V is the software development component and tests are carried out in the upward slope of the V.
Benefits and challenges of the SDLC
A well-defined SDLC offers several potential benefits to development teams:
- A well-defined SDLC aids in avoiding possible mistakes.
- Teams using the SDLC can measure progress easily.
- The shorter each software iteration is, the easier testing can be.
- Using sprints in an SDLC model can aid in development speed.
However, if used less optimally, the SDLC can come with hindrances, such as the following:
- Some models require more resources than others.
- Not all models are optimal for specific environments.
- If a mistake is made in a planning stage, then it could mean delays in the software development stage.
- Not all models are easily adaptable.
Many advantages are specific to the chosen model. For example, Waterfall and Agile models offer different advantages. Waterfall methods have the advantage of being easy to understand, well defined and easy to verify in each phase. However, the Waterfall model does not allow for the start of the next phase until the previous one is finished, is not suitable for long-term projects and can get expensive if any changes are needed.
Meanwhile, Agile enables flexibility, is modular -- each iteration is separated by sprints -- and is well suited to both long- and short-term projects. However, Agile has high development costs, needs skilled teams and can be exhausting for teams to work on with constant sprints.
