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The Software Development Lifecycle (SDLC) describes the systematic approach to developing software. In this article, we’ll look at:

The SDLC to ensure appropriate protection for the information that the system will transmit, process, and store. Applying the risk management process to system development enables organizations to balance requirements for the protection of agency information and assets with the cost of.
Systems Development Life Cycle Checklists The System Development Life Cycle (SDLC) process applies to information system development projects ensuring that all functional and user requirements and agency strategic goals and objectives are met. The SDLC provides a structured and standardized process for all phases of any system development effort.
What Is the Software Development Life Cycle (SDLC)? The Software Development Life Cycle or otherwise called the application development life cycle, describes the processes involved in building an application, ranging from the planning phase to the deployment and maintenance phase.

The Software Development Life Cycle (SDLC) is a structured process that enables the production of high-quality, low-cost software, in the shortest possible production time. The goal of the SDLC is to produce superior software that meets and exceeds all customer expectations and demands. The SDLC defines and outlines a detailed plan with stages. SDLC, or Software Development Life Cycle, is a set of steps used to create software applications. These steps divide the development process into tasks that can then be assigned, completed, and measured. What is the Software Development Life Cycle?

What is the software development lifecycle?

The SDLC helps to ensure high quality software is built and released to end-users quickly and at an optimized cost. How you determine the quality of your software might vary, but general measurements include:

The robustness of the software functionality
Overall performance
Security
Ultimately, the user experience

Regardless of which software development you subscribe to—Agile, Waterfall, or other variations—this lifecycle can apply.

Who uses the SDLC?

Not so long ago, Watt S. Humphrey, known as the father of quality in software, remarked:

“Every business is a software business.”

More recently, Microsoft CEO Satya Nadella repeated the quote: “Every company is a software company”.

Of course, we can point to many specific technology companies who develop software. If there’s an app, someone developed it.

10.5 differential equationsap calculus. But business organizations that aren’t “in software” rely on on software and technology to do business (which is to say, all of them). These organizations will need to adapt at least some off-the-shelf solutions, likely to tweak software to align and optimize with their unique business operations.

That’s why people beyond developers or engineers should understand the SDLC approach: many stakeholders might be involved in various stages. Plus, cross-functional teams might adopt the SDLC to collaborate on Agile- and DevOps-based projects. Following modern SDLC practices and frameworks can significantly improve the software development process.

So, who uses the SDLC? In short, everyone.

Stages of the SDLC

The SDLC follows a series of phases involved in software development. Depending on the SDLC framework, these phases may be adopted sequentially or in parallel. (More on this below.)

The SDLC workflows may involve repeated transitions or iterations across the phases before reaching the final phase.

Phase 1: Requirement Analysis

The initial stage of the SDLC involves stakeholders from tech, business, and leadership segments of the organization. In this initial state, you’ll:

Analyze and translate business questions into engineering problems by considering a variety of factors: cost, performance, functionality, and risk.
Evaluate he broad scope of the project and then identify available resources.
Consider project opportunities and risks across the technical and business aspect for every decision choice in each SDLC phase.

This stage may continue for a prolonged period and includes provision for strategic changes as the SDLC evolves.

(Learn how to write software requirements specifications, also known as SRS.)

Phase 2: Feasibility Study

During this stage, evaluate the requirements for feasibility. Not every single requirement will be feasible for your current scope. The goal of this stage is to quantify the opportunities and risk of addressing the agreed requirements with the variety of resources and strategies you have available.

The feasibility study evaluates the following key aspects, among others:

Economic: Is it financially viable to invest in the project based on the available resources?
Legal: What is the scope of regulations and the organization’s capacity to guarantee compliance?
Operational: Can we satisfy the requirements within scope definition according to the proposed operational framework and workflows?
Technical: What is the availability of technology and HR resources to support the SLDC process?
Schedule: Can we finish the project in time?

Executive decision makers should answer and document these questions and study them carefully—before proceeding with the software design and implementation process.

Phase 3: Architectural Design

Next, the appropriate technical and business stakeholders document, review, and evaluate the design specifications and choices against the risk, opportunities, practical modalities, and constraints.

In this phase, you’ll have technical documentation that specifies:

Systems architecture
Configurations
Data structure
Resource procurement model

Desired output can include prototypes, pseudocode, minimal viable products (MVPs) and/or architecture reports and diagrams that include the necessary technology details:

High-level design details include the desired functionality of software and system modules.
Low-level design details can include the functional logic, interface details, dependency issues, and errors.

Phase 4: Software Development

Implementation follows the design phase. Several independent teams and individuals collaborate on feature development and coding activities. Frequently, individual developers will build their own codebase within the development environment, then merge it with the collaborating teams in a common build environment.

While the requirements analysis and design choices are already defined, feedback from the development teams is reviewed for potential change in direction of the design strategies.

This is the longest process in the SDLC pipeline and it assists subsequent phases of software testing and deployment.

(Explore behavior-driven development, one approach to developing software.)

Phase 5: Testing

In this phase, you’ll use testing to:

Investigate the performance of the software
Discover and identify potential issues to fix or address

Testing teams develop a test plan based on the predefined software requirements. The testing plan should:

Identify the resources available for testing
Provide instructions and assignments for testers
Select types of tests to be conducted
Determine what to report to technical executives and decision makers

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Testers often work collectively with development teams and rework the codebase to improve test results.

It is very common for teams to repeat the development and testing phases several times, before moving onto the final stages of deploying and and releasing the software.

(Consider the benefits of testing automation and testing frameworks, like regression testing, BDD, and TDD.)

Phase 6: Deployment

You’ve reached the final phase of the SDLC pipeline when your finished product has passed the necessary tests. Now, make it available for release to end users in the real environment. Several procedures and preparation activities are involved before a software product can be shipped, including:

Documentation
Transferring ownership and licensing,
Deploying and installing the product on customer systems

(Learn more about the deployment and release stages.)

Traditional vs modern SDLC methodologies

With traditional SDLC methodologies, such as Waterfall, these phases are performed independently in series by disparate teams. Under the Agile methodology, these phases are performed in short, iterative, incremental sprints.

An SDLC pipeline and framework can be as varied as the number of organizations adopting them—virtually every company tries to adopt a strategy that works best for their organization.

In today’s era of software development, however, these stages are not always followed sequentially. Modern SDLC frameworks such as DevOps and Agile encourage cross-functional organizations to share responsibilities across these phases conducted in parallel.

For instance, the DevOps SDLC framework encourages Devs, Ops, and QA personnel to work together for continuous development, testing and deployment activities. Additionally, the testing procedure is shifted left and early in the SDLC pipeline so that software defects are identified before it’s too late to fix them.

History of the SDLC

The profession of “software developer” has existed since the first computers, and their operators, as far back as the days of ENIAC and vacuum tubes. Practices and methods for developing software have evolved over the decades since the invention of the computer.

Those methods have adapted to the state of the art in computer hardware, development tools, and modern thinking about the organizational management of software development teams. With this progress, new methods of software development have grown out of private and public software development efforts around the world.

These methods vary widely in approach, yet they share a common goal: to develop software as cheaply, efficiently, and effectively as possible.

What is the SDLC?

Software is a complex product that is developed and delivered through a series of steps. That is the one thing all the various methods have in common: one way or another, software, like all products, starts as an idea. The idea then becomes a document, or perhaps a prototype, depending on the method in use.

Whether a document, diagram, or working software, the artifact created in one step becomes the input to the next step. Eventually, the software is delivered to the customer. The sequence of steps used by these methods is commonly referred to as the Software Development Lifecycle (SDLC.)

How does the SDLC work?

The process of software development is a never-ending cycle. The first release of a software application is rarely “finished.” There are almost always additional features and bug fixes waiting to be designed, developed, and deployed.

Reports from error monitoring software about usability and bugs feed back into the process of software development, and become new feature requests and improvements to existing features. This is why the Software Development Life Cycle is the most general term for software development methods. The steps of the process and their order vary by method. Regardless of method, they typically run in cycles, starting over with each iteration.

Benefits of the SDLC

“If you fail to plan, you are planning to fail” - Benjamin Franklin

It’s very difficult to carry out a complex, team effort such as software development without some kind of plan. Each software development methodology (several will be detailed below) is a plan framework for how to develop software. There is much debate about which method is best overall, which is best suited to a particular type of software, and how to measure success in software development. One thing, however, is certain: any plan is better than no plan.

Without some kind of structured plan, software development teams tend to devolve into a “herd of cats.” Developers don’t know what they’re supposed to create. Project managers have no idea how much progress is made towards completion of a project. Without a plan, the business doesn’t even have a way to decide whether the final product meets their requirements.

A formally defined method for software development in the form of the SDLC achieves a number of benefits:

A common vocabulary for each step
Defined communication channels between development teams and stakeholders
Clear roles and responsibilities among developers, designers, business analysts, and project managers
Clearly-defined inputs and outputs from one step to the next
A deterministic “definition of done” that can be used to confirm whether a step is truly complete

The Seven Phases of the SDLC

These steps are (very) roughly the same from one methodology to another. They tend to occur in this order, though they can also be mixed together, such that several steps occur in parallel.

As we’ll discuss later, Agile methods tend to “wind together” all of these steps into a tight, rapidly-repeating cycle. Waterfall methods tend to take each of these steps in turn. Outputs from one become inputs to the following step.

1. Planning

The planning phase involves aspects of project and product management. This may include:

Resource allocation (both human and materials)
Capacity planning
Project scheduling
Cost estimation
Provisioning

The outputs of the planning phase include: project plans, schedules, cost estimations, and procurement requirements. Ideally, Project Managers and Development staff collaborate with Operations and Security teams to ensure all perspectives are represented.

2. Requirements

The business must communicate with IT teams to convey their requirements for new development and enhancement. The requirements phase gathers these requirements from business stakeholders and Subject Matter Experts (SMEs.)

Architects, Development teams, and Product Managers work with the SMEs to document the business processes that need to be automated through software. The output of this phase in a Waterfall project is usually a document that lists these requirements. Agile methods, by contrast, may produce a backlog of tasks to be performed.

3. Design and prototyping

Once the requirements are understood, software architects and developers can begin to design the software. The design process uses established patterns for application architecture and software development. Architects may use an architecture framework such as TOGAF to compose an application from existing components, promoting reuse and standardization. Our friends bike across the united states for a great cause.

Developers use proven Design Patterns to solve algorithmic problems in a consistent way. This phase may also include some rapid prototyping, also known as a spike, to compare solutions to find the best fit. The output of this phase includes:

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Design documents that list the patterns and components selected for the project
Code produced by spikes, used as a starting point for development

4. Software development

This phase produces the software under development. Depending on the methodology, this phase may be conducted in time-boxed “sprints,” (Agile) or may proceed as a single block of effort (Waterfall.) Regardless of methodology, development teams should produce working software as quickly as possible. Business stakeholders should be engaged regularly, to ensure that their expectations are being met. The output of this phase is testable, functional software.

5. Testing

The testing phase of the SDLC is arguably one of the most important. It is impossible to deliver quality software without testing. There is a wide variety of testing necessary to measure quality:

Code quality
Unit testing (functional tests)
Integration testing
Performance testing
Security testing

The best way to ensure that tests are run regularly, and never skipped for expediency, is to automate them. Tests can be automated using Continuous Integration tools, like Codeship, for example. The output of the testing phase is functional software, ready for deployment to a production environment.

6. Deployment

The deployment phase is, ideally, a highly automated phase. In high-maturity enterprises, this phase is almost invisible; software is deployed the instant it is ready. Enterprises with lower maturity, or in some highly regulated industries, the process involves some manual approvals. However, even in those cases it is best for the deployment itself to be fully automated in a continuous deployment model. Application Release Automation (ARA) tools are used in medium and large-size enterprises to automate the deployment of applications to Production environments. ARA systems are usually integrated with Continuous Integration tools. The output of this phase is the release to Production of working software.

7. Operations and maintenance

The operations and maintenance phase is the “end of the beginning,” so to speak. The Software Development Life Cycle doesn’t end here. Software must be monitored constantly to ensure proper operation. Bugs and defects discovered in Production must be reported and responded to, which often feeds work back into the process. Bug fixes may not flow through the entire cycle, however, at least an abbreviated process is necessary to ensure that the fix does not introduce other problems (known as a regression.)

Software Development Life Cycle infographic

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Popular SDLC models

The two best-known methodologies within the SDLC are Waterfall and Agile. Below is a brief explanation and how they relate to the SDLC.

Waterfall

The Waterfall method of software development follows a rigid, predetermined path through a set of phases. This method was adapted from traditional engineering. Ironically, the paper credited as the origin of the Waterfall method, describes it as being fundamentally flawed. The method that is known today as “Waterfall” was mistakenly derived from a misunderstanding of this original work. Despite that fact, Waterfall became a very common, even standard methodology for large projects around the world.

Waterfall methodology begins with long planning and design phases. Once developed, the software then goes through phases of testing, and is finally deployed for use. Waterfall is considered by many to be too rigid to adapt to changing requirements. It does not support feedback throughout the process, leading to the implementation of requirements that may have changed during the development effort. This weakness in Waterfall led to the development of more flexible methodologies, such as Agile.

Agile

The Manifesto for Agile Software Development was drafted and signed by a group of software developers in 2001. Reading the manifesto, you can see clearly the contrast between Waterfall, then the de-facto standard for development methods, and Agile, the newer method.

The Manifesto addresses key problems with Waterfall that led to challenges in software delivery. Where Waterfall tends to be a “one-way road,” Agile is a more flexible framework that allows for uncertainty. Agile emphasizes teamwork, prototyping, and feedback loops that can change the direction of the development effort in response to changing requirements.

Several variants of Agile have emerged since the signing of the Manifesto. Scrum defines specific roles and events, known as ceremonies, as part of its practice. Kanban is simpler, with fewer prescriptions and more flexibility. Agile teams often combine these together to adapt a bespoke process that fits them best.

SDLC Practices

Waterfall is still used by many companies around the world, however, Agile is rapidly gaining ground. Regardless of the method used, there are practices that reduce risk and increase the chances of success.

Source control

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The importance of a central source control repository cannot be overstated. Development teams that do not use source control are taking risks, both with the code, and their process. Using source control reduces risk by ensuring that work (code) is gathered together in a single place, on a regular basis. If a developer workstation or file server fails, the central repository saves the day. Modern Source control systems also support Continuous Integration.

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Continuous integration

The purpose of Continuous Integration (CI) is to keep the software in a functional state. Prior to the common use of CI, development teams would write thousands of lines of code, then attempt to integrate them. This integrating that much work all at once is tedious, painful, and prone to error. CI is an automation that builds software every time the code changes. If there is a problem, the CI system alerts the developers. Following proper CI practices, no further work is done until the build is successful. This prevents errors and defects from progressing into software that should be as bug-free as possible.

SDLC Management systems

Large, complex software development efforts can be unwieldy and difficult to track. An entire class of software systems has grown around this problem: Application Life Cycle Management. The larger the effort, the more indispensable these systems become. They offer features in work management, bug tracking, and analytics to assist in decision making.

Conclusion

All software begins as a concept, and flows through a series of phases until a release is developed and deployed. The Software Development Life Cycle of an application or system continues, with updates and new features, until the day it is decommissioned or replaced. Several methods for software development have evolved over the decades.

Waterfall methods are still common, though Agile is rapidly overtaking it in companies large and small. Whichever method you choose, use the right tools for the job. Software is difficult to delivery reliably without them. There is no perfect method, but it’s far better to use some method than none.