Software development is an intricate process that extends far beyond just computer programming. Each software development project requires detailed research, planning, design and architecture to ensure that user needs are captured and accurately represented in the final product. Newly authored code must face a battery of tests before it can be fully integrated into the main repository, and the bulk of the effort and cost will come from ongoing maintenance of the application. Together, all of these activities make up the software life cycle.
The software life cycle, sometimes referred to as the software development life cycle (SDLC) can be summarized as the set of steps, tasks, activities, and processes that are required to develop a new application. The software life cycle can be defined in many different ways and each development team is free to customize their own development process to fit their unique needs and circumstances. Still, the typical software life cycle can typically be summarized in eight or ten stages.
The software life cycle has changed and evolved as developers create new paradigms and working methods for delivering software applications. Still, there are concrete benefits associated with the adoption of the software life cycle model as a guide for software development activities.
The software life cycle is both descriptive and prescriptive. It describes how a software application is developed, beginning with the initial identification of a need, demand or market opportunity and finishing with the operation and maintenance of the application by developers. The model also serves as a methodological framework for software developers pursuing a structured approach to application development. While the software life cycle can be represented in different ways, we choose this eight-step model that covers the most important activities of software development.
The first step of a successful software development project is demand identification. Before a team of developers can begin to collect user needs to start establishing requirements, they must first choose a target user for the application. This entails the identification of a target market, a market opportunity, or some unmet demand in the marketplace. Demand identification is really about finding a customer or user base whose needs you can address through the development of the application.
Demand identification can happen as a result of market research or when a firm interacts with its existing users and customers.
Requirements Engineering/Capturing User Needs
Once a software development team identifies a need for an application in the marketplace, the next step is to understand the specific needs of users. This process is called requirements engineering and its purpose is to establish the "scope of work" for the project and to understand and detail the features and functions that users will expect in the application.
Software & Code Design
Once a scope of work has been clearly defined through the requirements engineering process, the project team will create a thorough scope-of-work document that includes all of the user requirements captured from the customer. The next step is to actually design the application. A systems designer will create specifications for the software, establish specifications for the hardware that it will run on and define overall system architecture for the creation of the application.
Software designers sometimes put forward more than one proposed architecture for the application in a document known as a Design Document Specification (DDS). This document can be presented to stakeholders who would formally assess each plan on the basis of time, budget and risk to determine how best to proceed.
In the programming stage of the software life cycle, teams of software developers work together to write the application code in accordance with the specifications created during the design stage. Teams of programmers are not only responsible for writing code, but they may also be responsible for producing documentation, writing unit and functional test scripts for the code and ensuring that it is free from bugs.
The programming stage begins to introduce increased variability in how projects are delivered. Some projects are coded with a monolithic architecture and others are coded using a microservice architecture. Some development teams work in the agile paradigm and may code individual features of the application in condensed time blocks known as sprints. Others do all of the code development for the whole application at once during the programming stage.
Testing and Integration
Once programming teams have completed all of the features or modules necessary for the application, the modules must be tested and integrated to create a stable version of the final product. The software can be tested in many different ways, but at the minimum, there should be:
- Unit Testing - A unit test ensures that a single module or piece of code is functioning correctly. These are the simplest type of functional testing.
- Integration Testing - Once all of the modules of an application have been integrated, integration testing is used to verify and validate their combined functionality.
- User Acceptance Testing (UAT) - UAT puts the application in front of clients and verifies that the end-to-end process flow of the application matches the business requirements set forth by the customer early in the software life cycle.
A large application produced by separate development teams can face significant challenges in the integration stage. New working methods like continuous integration and continuous delivery are being used to reduce the time spent in the integration stage of the SDLC.
Before the software application can be made available for users, developers may prepare some documentation to describe the functioning of the application and help users navigate the interface to take full advantage of features. Project documentation can also include test scripts and APIs.
When all errors have been detected and removed, the newly developed application can be deployed to a production environment and made available for users. An increasing number of organizations are choosing to deploy applications into public and hybrid cloud environments, taking advantage of the low IT infrastructure costs made possible by dedicated cloud service providers.
Operations & Maintenance
Software development teams working in the DevOps paradigm may also be responsible for maintaining and operating the applications they build, including producing patches and updates, releasing new improvements and producing changes in response to user needs and requests. Application maintenance is the most costly portion of the software life cycle, beginning once the software is deployed and continuing on throughout the entire operational life span of the application.
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