Software engineering has many SDLC models. Choosing the right one is half of the battle for a successful product. Software development methodologies are a set of frameworks that allow for efficient project management. We’ll be looking at the most popular ones, examining the steps involved, and discussing how to select the best option based on the requirements.
What is the software development lifecycle? Why does it seem so complicated and difficult at first glance? Software development life cycle (SDLC) is one of the most fundamental concepts of software development. Software Development Life Cycle is the acronym. SDLC is a continuous, ongoing process that begins when the decision is made to launch the project and ends when it is removed from exploitation. There is no one universal SDLC model. They are divided according to various factors. Each approach has its strengths as well as weaknesses.
Their variety has significantly increased since the original “waterfall” SDLC model. There are many product types that make up the SDLC model’s diversity, from web app development to complicated medical software. If you use one of these SDLC models as a basis, in all cases, it should be modified to reflect the features of your product, company, or project. Below is a list of the most popular and reliable SDLC models:
The SDLC models describe how the process is structured, which order potential risks are eliminated and what solutions are found. We will look at some models, compare their differences and identify the best and most comfortable models.
The SDLC model also defines the frequency of communication among programmers as well as other details that relate to collaboration within a group. The project manager should select the right model for the team size and working schedule.
Software development lifecycle models of the adaptive type, for example, are not suitable for large teams. They will only yield results in small groups of 5-10 people. We’ll be discussing two types of SDLC models in a later article: “Adaptive and predictive” and “heavyweight, agile”.
No matter which software development method you choose, there are core stages that every software product must go through. These stages are essential for understanding the SDLC models. Let’s take a look at them.
SOFTWARE DEVELOPMENT LIFE Cycle: PHASES
Software engineering has many SDLC models. They vary depending on many factors. The sequence of phases in the software life cycle is generally the same except for a few exceptions. Let’s look at the software life cycle phases and what to do during each.
Stage 1. Planning And Requirement Analysis
Software life cycles require analysis and requirement gathering. This stage involves many people and many processes. Specialists try to see the project from a business perspective so they can decide if it is worth the investment.
Every software development cycle begins with an analysis. This is where all stakeholders discuss the requirements of the final product. This stage aims to define the system requirements in detail. It is important to make sure that everyone involved in the process understands the requirements and how they will be implemented. QA specialists are often involved in the discussions. They can also interrupt the development stage with adjustments if necessary. A project manager also defines the technologies, team load, limits, time frames, budget, and timelines. These requirements will guide the project manager to make the best decisions.
This stage is where the business analysts play the most important role. They communicate with clients, hold meetings and answer questions. It is important to get a clear application concept, to document it and to present it to the team for the next stages.
Let’s be more specific and name the deliverables at this stage. The business analyst, along with the project manager does the cost estimate and determines the scope of the work. The requirements will vary depending on the software development model. They may be extremely strict or not enough to begin the work. The project manager should create the initial work plan and divide all tasks between team members.
Specialists should take requirement analysis seriously because it is the foundation for all future work.
Stage 2. System Design
The system design phase is basically an extension of the plan that was developed in the first phase. All the information about the product is being analyzed, and then systematized. The requirements analysis phase was primarily written in plain English. At the design stage, technical details are added to the plan.
This is the phase in which the developers design the architecture. All stakeholders are involved in this phase, which includes the customer.
Software engineers, database specialists, and designers are some of the experts who actively participate in this phase. Software engineers, system architects, database specialists, designers, and PMs are all part of the software development process.
The system design stage delivers system architecture and wireframes, mockups of app screens and wireframes. Documentation is required for every system component that is created.
Stage 3. Development
Once the requirements have been approved, the process moves on to actual development. This is the longest stage of the SDLC. All information regarding the product has been collected and is well-planned and designed. The developers’ job is to combine them into a working infrastructure and put them into code. They then begin to write the source code, keeping in mind all requirements. The software environment is adjusted by the system administrators. Frontend programmers create the interface and logic that allows the program to interact with the server.
Because the functionality must match the design, programmers communicate regularly with designers. Designers might change something in mockups or make minor adjustments to the features’ implementation.
Programming itself is divided into four stages.
- Algorithm Development
- Writing source code
- Compilation
- Debugging and testing
The PM is responsible for ensuring that documentation, system design and other components are in compliance with the applicable standards. He also manages teams and ensures consistent product delivery.
Before moving to the next phase, programmers must code the front-end and back-end. Once all the above is done, the team can move on to the testing stage.
Stage 4. Testing
The debugging phase is part of the testing phase. Here are all the errors in code that were missed during development. These issues are documented by QA specialists and passed back to developers for correction. This process continues until all critical issues have been resolved and the software workflow has become stable.
Depending on the testing methods used by QA engineers, the activity in this phase can vary. These methods are used to perform manual testing.
- Acceptance
- White-box testing
- Grey-box testing
- Black-box testing
- Unit testing
- Integration testing
Automated testing is a preferred option for QA professionals. They use many frameworks and solutions to make the process easier.
Only after the app demo is made public, can QA engineers receive testing results. They can also interact with the app as users. It helps you to determine if the product meets your business needs as well as technical requirements.
Stage 5. Deployment
Once the program has been finalized and is free of any critical issues, it’s time to release it for end-users. The tech support team is formed after the program’s initial version release. This team collects feedback from users and analyzes it. They consult with users and offer support during exploitation.
DevOps engineers are responsible for app deployments and releases in Agile development. To facilitate release processes, DevOps experts use the CI/CD principles of continuous integration and delivery. There are several responsibilities that they have:
- Automating the delivery process
- Management of source code
- Code containerization
- Configuration management
DevOps engineers make use of a variety of tools to speed product deployment, such as Jenkins and Docker.
Sometimes the DevOps team may include 3 to 5 specialists. Separate people are responsible for release management, automation and QA oversight, as well as security management. In some cases, however, one person is able to take on all these responsibilities.
The product manager is responsible to analyze the data collected based on real user feedback. This allows a team to draw conclusions about which practices are most successful and which ones need to be replaced.
This information is useful for a product manager or business analyst to determine if certain features are required or not. This information gives them a clear picture about what people want. After the initial release, it is not unusual for an application to be modified.
If we break it down roughly, maintenance includes two types: support for functionality that was initially created and adding new features. It usually involves a maintenance agreement. This defines the software provider’s responsibilities. This document focuses more on the support of existing features. It outlines how many consultations and departures are allowed to clients when it is convenient for them to contact the team, and other details. This document also addresses the frequency of software upgrades.
A project manager reviews the feedback from the initial release to determine the technical aspect of the issue and assigns developers to fix bugs or add updates. DevOps engineers often implement minor changes and make important updates according to a set schedule.
DevOps specialists plan and schedule the release while programmers fix bugs or add new features. DevOps releases the new version to the app distribution platform, or server, if we are talking about web apps.
This means that if support and maintenance is completely entrusted solely to the software developer provider, there are no timeframes. Customers may also take care of product maintenance, but they should only contact a service provider in very urgent cases.
Types of SDLC MODELS
When it comes to the classification of SDLC model and methodology models, there are many options. Let’s now see the main types.
Heavyweight and lightweight processes
There are two main lifecycle models for software development: lightweight (agile) and heavyweight (predictive). Pre-defined scope of work for heavyweight processes is a sign that they are pre-defined. They are often called predictive. These require significant programming contributions and extensive documentation. Companies have traditionally chosen a heavyweight approach to streamline large projects and organize them. This type of SDLC model is no longer popular. This model is prone to reducing project efficiency due to excessive bureaucracy.
It is being replaced by adaptive, or lightweight, processes. These are a compromise between excessively strict discipline or its complete absence. Agile methods require less documentation for the software life cycle.
An adaptive approach, for example, considers customer requirements such as the need to constantly modify applications. With the emergence and unplanned changes, predictive SDLC models are becoming more complex.
When there are strict requirements and large teams, heavyweight methods can be useful. Agile strategies are best used in small groups, with up to 10 people working together in a team.
Predictive SDLC Models
These models are predictive (heavyweight).
- Waterfall
- Iterative
- Spiral
- V-shaped
There are many other options, but these are some of the most popular. Let’s look at the key characteristics of each. Because they are very similar, we won’t go into detail about the phases of each model. Let’s now examine the pros and cons of each model.
Adaptive SDLC Models
The brightest candidate among the many SDLC models and methods is adaptive (or agile). The agile approach opens up new opportunities for specialists, allows more flexibility, and places communication between people above blind plan following.
These models have been realized in the following:
- Scrum
- XP
- Kanban
We’ll be looking at each one in more detail later in this article.
SDLC MODELS
Waterfall SDLC Model
The waterfall is a cascade SDLC modeling that shows the development process as a flow. It moves step-by-step through the phases analysis, projecting and realization, testing, implementation and support. Each stage is gradually executed in this SDLC model. Waterfall implies strict documentation. Each phase of the SDLC model is predefined.
The waterfall life cycle model has been regarded as one of the most effective ways to manage complex projects. This method allows you to avoid many errors that could arise from insufficient control of the project. It does however result in extensive documentation development. Although it is beneficial for the developers working on the product in the future. However, it can take a lot of time to record everything.
Sometimes, the feedback loop may be included. This loop allows for quick reviews of each stage’s results and minor modifications. This loop allows specialists to quickly return to the previous stage.
A team should not make any significant changes to their initial plan until the last stage. This will allow them to go back to the beginning and complete all phases of the software lifecycle.
Use Cases for the Waterfall SDLC Model:
- These requirements are clearly documented
- Product definition is stable
- Predefined technologies stacks are not dynamic.
- No ambiguous requirements
- The project is very short
SDLC Model for Iterative Use
Although the iterative model is similar to a waterfall model in appearance, there are significant differences between them. Let’s say that an app has ten core features. The waterfall model will have all ten functions planned out during the requirements analysis and design phases, and then implemented in the development phase. Iterative models are quite different. This implies that developers create a limited number features during each iteration of the entire process.
The Iterative SDLC model doesn’t require a list of all requirements to be completed before the project can begin. The requirements for the functional component may be the first step in the development process. These can be added later. This repetitive process allows for new product versions every cycle. Each iteration, which lasts between two and six weeks, involves the development of a different component of the system. This component is then added to the earlier features. In math terms, iterative modeling is the realization of the sequential approach method. It means that the final product shape will be gradually closer to reality.
The team decided that they would work on three of the 10 features during the initial iteration. They go through all phases of the software development cycle, from requirement gathering to deployment and maintenance. The development cycle begins again when they move on to the next set.
Use Cases for the Iteration Model:
- From the beginning, the requirements for the final product will be clear
- This project is complex and large.
- Although the main task has been predetermined, details can change during the process.
This method results in continuous learning. The team observes and then brings new ideas to each iteration.
Model Spiral SDLC
The Spiral model is a mixture of the Iterative SDLC and Waterfall SDLC models, with a strong emphasis on risk analysis. The key problem with the spiral model is how to determine the appropriate moment to move on to the next stage. This problem can be solved by using the preliminary set timeframes. Even if work has not been completed on the previous stage, the plan is followed to move to the next phase. Based on statistical data from previous projects, and even the experience of the individual developer, the plan is created.
Use Cases for the Spiral Model
- The customer isn’t certain about the requirements
- During the software development cycle, there are significant edits to be made.
- Project risk management is essential
SDLC Model in V-Form
The architecture and work approach are what make the V-shaped algorithm different from other ones. This model is different from the waterfall and iterative ones in that we can see one additional axis. They form the V letter, along with the first. It is visible in the image below.
This is the V-model because of its appearance and primary priorities: Validation and Verification. The verification stages are located along the left axis, while the validation phases are on the right.
Let’s clarify the terms so that there are no misunderstandings. Although they may seem very similar, validation and verification are two different terms. Verification is used to verify that the software meets the technical requirements. Verification, on the other hand, confirms that the product meets the business requirements, serves its intended purpose and acts as expected. Verification accounts for aligning features to the technical requirements based upon the business requirements. Validation is responsible for the last two.
These concepts cover different types of product testing. These methods can be found along the respective axes. The associated one is on the right. The requirement analysis stage corresponds, for example, to acceptance testing, system design, system testing, and architecture design, as well as integration testing.
The V-shaped SDLC Model is an extension of the waterfall model and it’s based upon the associated test stage for each development stage. This model is rigorous and the next stage is only started after the previous one has ended. Each phase contains the current process control in order to make the transition to the next stage possible.
Use Cases for the V-shaped Model:
- Projects that require product testing
- For small and medium-sized projects where the requirements are very specific
- It is easy to find the engineers and testers required for the required qualification
Agile SDLC Model
Agile is not a development method, but a philosophy. It encompasses a variety of methods. The most popular realizations of Agile SDLC include Kanban, Scrum, and XP (extreme Programming). Let’s first look at the core principles of Agile and then briefly examine some of its realizations.
The first thing that makes it unique is the way all work is divided into iterations, such as the iterative model. These iterations are called sprints. In the beginning, each team determines what actions they will need to complete within a given time frame. This iterative approach has one major difference: the amount of work isn’t fixed and can be modified at any time.
Agile never leaves customers in ignorance. The client is always in touch with specialists on the provider’s side. They keep the client informed about the progress of the work and help him to understand the plan. All changes are discussed with the customer, and he approves them. Before the development team can move onto the next stage of Agile, each stage must be thoroughly reviewed and agreed to by all parties.
Agile also includes Sprint reviews and daily or weekly calls. Sprint reviews follow this structure: the first half of the meeting is dedicated to the performed work and the second half for planning the next Sprint.
Face-to-face communication is another aspect of the Agile software cycle. It is one of 12 Agile principles. Agile provides video conferencing to help customers understand the body language, despite the fact that many companies outsource. It can help avoid misunderstandings and foster better client relationships.
There is much more to Agile SDLC. But let’s focus on specific numbers. Amazing results were found in the research on Agile methodology. These are the key points.
- Agile adoption has increased from 37% to 86% by 2020 to 86% by 2021
- Agile helps you achieve 50% more business goals
- 70% of people choose Agile because they can change project priorities at any time.
- 60% of programmers who use Agile report a faster time to market
Use Cases for the Agile Model:
- Users’ needs are constantly changing
- Because of the many iterations, the cost of the modifications is less
- To start a project, you only need to plan.
The agile methodology allows customers to see the final product and decide if they are satisfied or not. This is one advantage of agile software development. It is not possible to accurately estimate the development costs and resources without having defined requirements.
Agile methods offer flexibility, which is a plus. It can also be a disadvantage. If developers aren’t well-versed in Agile, they may run into some problems. To learn more about the 10 most frequent mistakes in Agile development, you can read this article.
Let’s take a look at the most common realizations of Agile SDLC and how they are organized.
Scrum/XP
Scrum and Extreme programming are two of the different versions of Agile. They make a great approach to software development. But, it’s not the same thing. Scrum is a method of project management, while XP is a technique for software development.
Extreme programming focuses on the technical aspects of software development. These include continuous integration and pair programming. Scrum is, in turn, oriented towards the organization and management of the process.
Scrum is built around sprints. Sprints are iterations that last between 2 and 4 weeks. It begins with product planning and then an iteration. Next, the product must pass the stages of the chosen software development method (XP is the most common option for Scrum). The team then delivers the final product. After that, it’s time to do the retrospective, which includes a sprint review and analysis.
Sprint planning, daily meetings, demos and reviews are the core methods of Scrum. Each sprint ends with a retrospective. Its core principles include courage, commitment to, focus, openness and respect.
Scrum, which is an implementation of Agile, must adhere to 12 Agle principles.
Scrum’s uniqueness is due to its transparency and apparentness. It is evident in the Sprint backlogs and product backlogs.
PB refers to a set or objectives that must be met at the end. The product backlog contains the names and priorities of each item, as well as the number of sprints in which they must be completed. Each item in the sprint backlog is broken down into smaller steps, called tasks. SB identifies all tasks developers must complete in a given sprint.
Traditionally, PB and SB were organized on a physical board called the Scrum board. It is divided into vertical sections. These are the ones that make up the product backlog.
- User story
- Priority
- Sprint
- The Task Owner
- Estimated Effort
- Status
Product backlog, as you can see is primarily focused on the organizational portion of the software development life cycle. Let’s look at the sections of a sprint backlog:
- User story
- To do
- In progress
- To verify
- Done
Each section is populated with sticky notes that contain relevant information. These boards are now being replaced by online spreadsheets. It is very efficient and illustrative.
Scrum does not specify the actions of developers, as you can see. Scrum is responsible for product delivery and organization. It should be combined with a methodology that is focused on the programming approach.
Scrum and XP are the most popular combination. Extreme programming is where weekly releases are better than an app delivered in one year. Unlike Waterfall, where developers and testers are separated, testers can work alongside developers throughout the entire process. This eliminates a lot of work in the testing phase and reduces the number of code changes. XP also means that all members of the team can share the code, so they can offer suggestions and see it from different angles.
Kanban
Kanban is another example of Agile. Although it is similar to Scrum, Kanban is a different version of Agile. Both methods use boards to track progress, and both have similar sections. Kanban’s are:
- Required
- In progress
- Done
Although the Kanban statuses are not as extensive as other systems, they are sufficient to allow software developers to keep pace with their work. The main differences are in the work approach and the core principles of Kanban.
Let’s begin with planning. Kanban does not obligate developers to follow the plan like Scrum. The plan is subject to continuous changes. Kanban allows team members to track time spent on tasks but not the exact amount. Instead, the board contains the “Recommended timeframe”. This section allows you to estimate the development time. Scrum also has clearly defined roles such as scrum master, product owners, and a development group. Kanban has no predefined roles, which allows for greater flexibility. Kanban iterations don’t have a set timeframe. They can change depending upon the amount of work.
Scrum is very flexible until you learn about Kanban, which allows even more flexibility. It’s not clear how effective this approach will be, as an unorganized team can be just as destructive as one that is well-organized. Before you decide on a method for software development, consider all the pros and cons.
HOW TO CHOOSE A SDLC MODEL
There is a high chance that you will get confused when choosing the right software development approach. It’s possible to learn more about each approach and it will all start to make sense. There are some key differences between each software development method that you can use. It is usually the project or delivery managers that decide which approach to use. This is made easier by their knowledge of the particularities of each method.
Let’s look at the logic behind choosing the right technique for your project. It’s important to consider:
- How exact are the requirements?
- How long the project takes
- The complexity of the project
- How big is your budget?
- What length the client would like the documentation to be
Once you’ve answered the questions, it is time to integrate your knowledge of software development techniques. Let’s quickly go through each question.
Agile software development is the best approach to addressing unclear requirements. Spiral and iterative models work well.
Agile is the right answer when time frames are short. Agile significantly reduces timeframes due to the ability to make changes at any time and work simultaneously on multiple features.
Agile may not be stable enough for large-scale projects, so some people still use it. Predictive models may appear to be more durable and long-lasting, which should theoretically lead to high product quality and quick product delivery. It’s almost impossible to plan a project for more than a year. It is impossible to predict every detail that might occur during the project’s course. Heavyweight methodologies are often subject to unexpectedly extended time frames. A subtle change in scope can cause a cascade of changes that could ruin all plans. This software development approach works well for smaller projects that have fewer requirements.
It is not a good idea to start software development using the V-shaped or Waterfall model when your budget is low. These models are expensive and require many cycle repetitions, which can increase development time and the budget.
The documentation is the key. As we’ve already discussed, the benefits of Agile are not all that great. However, it is important to remember that extensive documentation is not one of its strengths. If clients require detailed documentation, it is better to choose heavyweight methods like V-shaped, Waterfall, and Iterative.
Another important point to remember is that you can always optimize an existing model. It doesn’t mean you have to adhere to all the instructions. These instructions are there to help you, but you have the option of optimizing the time between stages or adding more if necessary.
CONCLUSION
Methodologies reduce the need for new management and development methods. They provide a framework to guide the software development process. They provide a clear plan for every member of the team so they all know what to do, why and what their final goal is.
To meet diverse development needs and expectations, different models were developed during the SDLC evolution. The world is shifting towards flexibility and less rigidity. Yet, agile approaches combine responsiveness with well-organized project management.