Software Development Life Cycle (SDLC), What is it?

September 8, 2020

What is the software development life cycle?

The Software Development Life Cycle (SDLC) describes a universal roadmap for software development. With its help, you can also navigate what tasks and in what order you need to solve in the development process.

In software engineering, there are different types of SDLC models. They are based on software development methodologies for example waterfall model,  spiral model,  agile model, etc.

How the SDLC works

Understanding and following the SDLC lowers the cost of software development while improving quality and reducing development time.

In addition, since almost any SDLC model implies a cyclical process, and therefore quality control and testing are carried out at every stage. Thus, the final product is of a much higher quality.

SDLC phases

In general, the structure of the software development life cycle consists of several stages.

Software Development Life Cycle
Software Development Life Cycle

1. Define requirements or discovery phase

The discovery phase is the first step in the creation of every digital product. During this stage, software requirements are formulated. It is necessary to conduct all preliminary research to understand the goals that need to be achieved as a result of the implementation of the entire project.

It is important to answer a number of very important questions about software like:

  • Who is it for?
  • What issues should it solve?
  • What does good service look like?
  • Who is our competitor?
  • Which resources do we need?

This is a vital step that should not be skipped.

2. Software design stage (design phase)

The main purpose of the software design is to create a detailed plan for the subsequent work. This stage includes:

  1. Architecture design. The design of a software architecture allows guaranteeing the flexibility and reliability of the product. Also at this stage requirements for infrastructure are determined based on the predicted load and workflows.
  2. Prototyping. An interactive prototype helps get a basic understanding of how the application looks and works. Any change and improvement at this stage are less costly compared to the ones done at the development.
  3. Non-functional requirements formulation. It is equally important to decide on the platforms on which the software will run: iOS, Android, web etc. Other technical requirements are also formed: tech stacks, programming languages, frameworks that are suitable for solving the assigned task.
  4. External dependencies investigation. Defining external integration that we need, for example, integration with IoT smart locks, or external data sources like a Google Maps API.
  5. Security requirements and solutions formulation. We design the product to be reliable and secure with the customer’s personal data and able to resist external influence. That includes the design of role system and authorization methods, data exchange protocols like SSL, and other...
  6. Composing user story mapping. This document defines the prioritization of product features and the order of their implementation.

Here you can read about the software product design stage.

3. Software development stage

At this stage, the project managers and development team starts to develop software. The designers give the final shape to the product, and the developers implement the functional modules.

The software development stage usually consists of several steps that are called sprints, each step contains coding and testing stages. The result of each sprint is the execution of one of the user stories that is written in user story mapping.

Documents developed at the product design stage can be supplemented and corrected during development. This is a fairly standard situation in software development. As a result, this is how the project documentation is formed.

4. Testing phase

It is a very important step of SDLC, Testing gives the guarantee that products can work steadily and correctly in different situations and on different devices.

Testing can be automatic or manual. However, in any case, the product should be tested under different loads and in different situations, as well as on different operating systems and different types of devices.

5. Operations & maintenance stage

The Operations and Maintenance Phase is the final (and ongoing) phase that maintains the system, including any regular updates and adjustments that may be required. In addition, this is the stage at which we can get feedback from real users.

The most common SDLC models:

Waterfall model

This SDLC model is the very first and uncomplicated one. Using this methodology, we complete one stage and then begin the next. Each phase has its own fixed implementation timeline, and all phases follow one after the other. The biggest disadvantage of this model is that it is difficult and expensive to make new changes to the product, especially at later stages. However, in a number of situations, this model still proves to be quite effective to this day.

Agile model

The agile model implies working in small cycles, each of which results in a new version of the product. Thus, there is a continuous improvement of the product, which allows to very quickly introduce new changes that were not envisaged at the beginning of work. Each new version of the product is tested and the feedback received is used to plan a new cycle.

Iterative model

This SDLC model assumes a progressive release of new product versions. At the same time, it is usually that the development of one version itself proceeds according to the waterfall model. The general concept of iteration allows you to get rid of the shortcomings of the classic waterfall model, but it can lead to a large cost of resources for the project.

V-Shaped model

This SDLC methodology, which is an extension of the waterfall model, implies additional testing at each stage of development. This is also called the verification phase. This model performs much better on small projects with low risks of changing requirements.

Big Bang model

In the Big Bang Model, there is practically no stage of collecting requirements and architectural design, all resources are thrown directly into development. This is a high-risk model and is only suitable in certain situations.

Spiral model

The spiral model is very flexible and in some ways similar to the iterative model in its focus on repetitive stages. However, the spiral model goes further and iterates through the planning, design, assembly, and testing phases, with incremental improvements at each step. As a result, it can reduce development costs and facilitate change management of requirements.

Which SDLC methodology choose?

The choice of an appropriate SDLC methodology depends on the objectives, resources, and parameters of the project implementation.

Advantages of the SDLC

  • By following the life cycle, you can articulate goals and challenges at each stage of the process. This, in turn, will facilitate resource planning and make the development process more predictable.
  • A clear structure and life cycle stages guarantee that tasks are completed in the correct order, the implementation of the functionality will follow after its design and the correction of deficiencies after testing. With proper project management, there will be no duplication of tasks, unnecessary work, and design errors.
  • Rigorous testing is an important step in the life cycle. Thanks to this, the customers of the software will receive a much better product.
  • Maintaining project documentation guarantees independence from the individual people in the project, and unexpected team changes do not have a strong impact on the overall project progress.
  • Complex software development projects carry a high risk of changes in the requirements for the final product. Following the milestones and using the test results as a basis for planning new iterations helps manage these risks.
  • A simple and clear scheme for organizing software development, expressed in one of the life cycle models, makes it possible to significantly facilitate project management, achieve the desired result, and get positive feedback from end-users.
  • The lack of a methodology can lead to the loss of critical elements in the development process: it can be architectural design errors that make product scaling impossible, or difficulties in localization, or whatever.
  • With all of the above, SDLC models are not the only options - they are just general guidelines. The stages of the cycle can be modified, the models can be combined with each other - all this is possible if it serves the best efficiency in project implementation.
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