Techopedia Explains Software Development Life Cycle (SDLC)
Let's look at a more intuitive way to approach the definition of the software development life cycle (SDLC). Think about the stages that software development goes through, from the very earliest fulminations of a project idea, to releasing that software live in a production environment.
Think of the SDLC as composed of various “way stations” on the way to full final development and release, with all of the user testing and other things that go on at the end of the process.
That's a good way to start thinking about what the SDLC is.
SDLC Key Takeaways
Here are some things that are going to be central to our explanation of the software development life cycle:
- SDLC encompasses: planning, implementation, testing, documentation, deployment and maintenance.
- Models shifted from traditional staged SDLC processes, to agile, and then to Devops.
- Agile and Devops as practices merged traditional staging in new and interesting ways.
- The cloud brought the arrival of web-delivered resources into the picture.
- Although SDLC is now much changed, the concept remains largely the same.
History of the Software Development Life Cycle
The consensus is that the SDLC as a framework developed in the 1950s and 1960s as computer science itself evolved quickly.
Prior to the second half of the 1900s, when the ENIAC and various other innovations moved the computing world forward quickly, computing really wasn't elaborate enough to need something like the SDLC. The first implementations of software technologies involved simple tools, like basic go-to lines and if/then statements.
Over time, the concept of structured programming brought in the need for developmental models and the SDLC was born.
The first early models were mainly defined by the stages.
Take a look at this infographic to understand this historic migration of practices from the waterfall to new DevOps and agile methodologies.
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Iterative and incremental practices led to prototyping in the 1980s, which led to various different types of innovations like spiral and V-model frameworks, and then into agile in the 1990s.
There are numerous ways to describe these changes over time, but the bottom line is that the software development life cycle began as a carefully staged process.
The waterfall remains the dominant model for these early software development life cycle frameworks. In the waterfall model, everything in one stage is completed before you move to the next stage. All planning gets completed before the project moves to implementation. All implementation is completed before the process moves to testing.
Then, as these frameworks evolved into agile, this idea broke down into a system where collaborative work changed workflows, and previously monolithic staging was sliced and diced into its composite parts. For example, testing could go on in different phases in different environments.
As a side note, testing was increasingly becoming automated as well.
In any case, the move from waterfall to other models, to agile and DevOps, brings us up to the current day, where the DevOps mentality is leveraging cloud architectures, micro-services and more to redefine what software development life cycle work means.
The major software development activities include:
The client has a vague idea of what is required. The sales department, software engineers and domain experts all collaborate to gather information about what the product should be, its purposes and how it is supposed to work. This analysis is often coupled by market surveys.
After a thorough analysis of the requirements and planning steps to reach the target, the abstract client idea is put into practice by a group of software engineers. A “Software Requirement Specification” (SRS) document is compiled to include everything that must be developed to complete the project.
During this phase, the overall system architecture is designed by defining the functionality of each module as well as their interaction with third-party modules.
Building and coding stage
The product is built and coded according to the company’s own standards. Designers follow a set of best practices and guidelines, and use the programming tools they have at their disposal to develop the product.
The code is tested to make sure it is free of bugs, adheres to the client requirements and correctly interfaces with other software products together with the underlying hardware.
Deployment and Maintenance
The final version of the product is released to the market. Maintenance is performed over time to change the system architecture according to future needs. This may require the addition of code or alteration of the existing code.
The above development process is streamlined by a series of models. The development team selects the best suitable model among several known ones. The different models are:
Developers state the requirements, analyze them, determine a solution and frame a software architecture, interface representation, and algorithmic details. Then they develop the code, test the code, deploy the software, and maintain it. The main problem with this model is that the requirement to correct errors should be known upfront and at an early stage. Otherwise, the whole process may continue in the wrong direction, which could negatively impact the cost of production.
V Shaped model
Is a variation of the waterfall model. It emphasizes the verification and validation of the product. All deliverables are testable and progress is tracked by milestones. Testing is implemented in parallel to the development phase.
A prototype is developed in the requirement phase and evaluated by end users. Based on user feedback, developers alter the prototype to satisfy user requirements. While this model finalizes the requirements easily, its use in the production environment might result in quality issues, thereby making the process of correction continue forever.
Makes use of both waterfall and prototype models. It adds 4th generation programming languages, rapid application development prototyping and risk analysis to the waterfall model. The system requirements are designed and a preliminary system design is created. An initial prototype is designed and tested. Based on the evaluation of test results, a second prototype is created. Subsequent prototypes are constructed to ensure customer satisfaction. The system is created based on the final prototype. The final system is evaluated and tested. Though this model reduces risk to a large extent, it may not meet the budget and is applied differently for each application.
Iterative and incremental SDLC model
Specifies and implements a part of the software, which is then reviewed and further requirements added and implemented in groups. Every release delivers an operational product presenting the customers with important functionalities first, lowering initial delivery costs. The risk of changing requirements is greatly reduced and customers are allowed to respond to each build. In spite of its strengths, this model requires good planning and early definition of the complete and fully functional system. It also requires well-defined module interfaces.
Agile development model
Is used for time-critical applications in organizations employing disciplined methods. It speeds up the life cycle phases and has reduced scope.
Magic box model
Is a Web application development model. It is the fastest way to finish the project with the least bugs as it provides the chance to alter the code and database structures.
There are a lot of moving parts. That's part of why companies started to hire scrum masters, to get teams together and quickly orient them to what's happening on the ground.
That kind of check-in ensures that even in the highly complex environment, everything is humming along.
About Software Development as a Service (SDaaS)
With all of the above in mind, Software Development as a Service, or SDaaS, refers to the vast range of services available from vendors who will take over aspects of the software development lifecycle process in some way, shape or form.
These companies may dedicate teams of individuals to managing the software lifecycle in a way that supports the client company based on discovery and participation.
Many of these systems rely on the agile method, because it can be very symbiotic with the nature of SDaaS. Because there's so much interactivity and interoperability, the client can routinely interface with the support vendor in ways that promote good results.
Vendors may have scrum masters and other practitioners available to guide development or deployment teams that deliver according to specific needs.
Some vendors characterize this as offering software development services with ongoing projected costs, in order to help clients to outsource, although many consider SDaaS to be different than the outsourced IT model.
All of the above helps to show why the software development life cycle is important and how it has evolved over time.
Think about this fundamental method of creating the apps, executables and software products we use on a daily basis.