7 Software Development Models: How to Choose the Right One?
Let's define the software development life cycle, make an overview of the 7 most used models, and find out their differences and benefits in project development.
Join the DZone community and get the full member experience.Join For Free
Software development models have been first introduced to the software development community no sooner than in the 1950s-1960s. At that time, it was quite a good practice to structure everything and programming was one of the processes that had to be planned.
Today, this process is much needed in everyday project management as without a certain flow of events, project development can be quite chaotic. Therefore, any activity from project planning and up to its release and maintenance has a conceptual framework everyone needs to use.
So, this article will be useful for you if you:
- Struggle with the undefined process of software development.
- Lack certain knowledge about the project management techniques.
- Search for a way to optimize and structure the development phase.
- Want to accelerate the delivery process.
- Reduce project risks.
- Shorten the project timeline and excessive costs.
Let's define the software development life cycle, make an overview of the seven potentially used models, and find out their differences and benefits in project development. Moreover, let's make a comparison of the software models in software engineering to find out which one might suit you best!
Why Are the Software Project Development Models Needed?
Every software outsourcing company has its software development lifecycle (SDLC), which usually encompasses the following phases of app development:
- Requirement Analysis
- Development and Testing
These stages mark the usual process of software project development from gathering client requirements to launching a fully-fledged product with 24/7 support. At present, companies prefer a personalized approach to their workflow, so there are several conceptual models that include these development phases. The models have their key principles, basic flows, and timelines pre-written and established, and, for this reason, we call them methodologies.
Currently, there are seven featured methodologies to pay attention to. These are:
- Waterfall Model
- Iterative and Incremental Model
- Spiral Model
- V-shaped Model
- Prototype Model
- Agile Model
- DevOps Model
The value of the software development process models lies in the process optimization and, as a concluding factor, team performance boost. Every model is quite specific and implementing it, the company should focus on the same working techniques, vision, mission, and tempo. That's why we have so many of them to find the one that will work for your company and will be easily adjusted to by your team.
This year, according to Statista, the most practiced software engineering process models worldwide are DevOps taking as much as 36%, then goes Agile covering almost 32% and the third leader is Kanban that is practiced by 13% of the IT community globally.
So, what are the software development models? What are the software engineering models types organizations use today?
What Are the Software Development Models and How Do They Work?
1. Waterfall Model
The Waterfall model is the first of the software project development models that have been introduced in the software development circles. It is also called linear as the model implies each stage to be completed before going on to the next one. So, the model goes linearly step by step giving no possibilities to overlap any stage. Schematically, it would look like this:
Genuinely, the model resembles a real-life waterfall that has a beginning and an end with water falling freely from the cliff without being interrupted or altered.
The Waterfall model is applied to the software development life cycle when it is most suitable for a certain project.
What Factors Contribute to Choosing the Waterfall Approach?
- Short-term projects.
- Clear, fixed, and well-documented requirements.
- Static technology that is understood.
- Stable product definition.
- A variety of resources for product support.
- Low Product Owner Involvement.
- Strictly-set timeline.
- Fixed budget that cannot be changed.
In all the other situations choose the other model to approach your project development.
The main advantage of Waterfall is that the model is in strict order with regards to the tasks carried out and their timelines. Due to being fixed, the tasks can be easily divided between software departments and monitored as to task completion. Clients may find the Waterfall Model a reliable approach as they will be aware of the whole process from the start till finish beforehand. As for the disadvantages of the Waterfall Model, there are some as well. For instance, Waterfall has no revision of a task. The farther the application development goes forward into the other stage the harder it is to go back and change its conceptual basics or documentation.
Waterfall Model Advantages and Disadvantages
2. Iterative and Incremental Model
In the Iterative model, the development starts with implementing several small requirements, and then the product is enhanced with the help of numerous iterations (incrementally). The process of enhancement goes on in increments (iterations) until the application features are complete and it is ready to be deployed. Developing only a small part of the software is a smart approach as you can easily review what was done, quickly identify further requirements and proceed with the implementation or provide some changes to the app and then proceed. Either way, you'll benefit from the solutions as every new iteration will bring you a new and better version of the software.
Unlike the Waterfall model, the Iterative Model allows carrying out multiple iterations at a time and receives the product output simultaneously. The key to success, which the model offers, is in validating the versions of the software and testing them according to the requirements. This allows a better understanding of where the team is at with the project, the product's functionality verification, and 100% confidence that the product will be a success.
Where Is the Iterative Model Applicable in Software Development?
- System requirements are clearly defined and fully understood.
- Additional requirements can occur with time.
- When the team learns new technology and works on the project simultaneously.
- Specific resources are to be used only when they are required for specific iterations according to the contract.
- When the business goals might change in the future due to high-risk features.
The biggest advantage of the Iterative model is that it allows finding feature and design flaws at the beginning of development. Working in iterations and validating every development cycle will result in a risk-free product with the ability to add or remove features as well as alter the costs and timeline of the final product. Besides advantages, we should talk about some of the minuses that are also present.
Iterative Model Advantages and Disadvantages
3. Spiral Model
The Spiral Model is a combination of the Iterative and Waterfall models. From the Iterative methodology, it took the cycled development, and from the Waterfall one, it borrowed a systematic approach and the ability to control the process. The biggest emphasis of the current model falls on risk analysis. Also, it delivers a project in iterations, which swirl around the spiral.
The Spiral Model is designed in 4 stages. The product under development passes all of these stages during its iterations, which are also called spirals in this methodology. The stages include:
- Construct (Build)
- Evaluation (Risk analysis)
Identification is the stage where it is best to gather business requirements. This is done in a basic spiral. The following spirals identify system, subsystem, and unit requirements. Besides gathering requirements, this stage is all about communication between the customer and the system analyst to understand what is required to deploy.
The design also starts in the basic spiral with the conceptual design and includes subsequent spirals with architectural design, logical design of modules, physical product design, and the final design.
The Construct (Build) stage is the development of the actual software product at each and every spiral. In the basic spiral, when the concept needs to be evaluated according to its feasibility, you should develop a POC (Proof of Concept) and try to obtain valuable customer feedback.
Getting aware of all the requirements and design details, we produce a numbered software working model (build) version. The customer reviews all the builds and gives feedback.
Evaluation (Risk Analysis) is a process of identifying, estimating, and monitoring the technical feasibility and management risks. For example, schedule overdue and cost overrun.
After the customer has evaluated the build, the next iteration comes forward. This one follows the linear approach to ensure the feedback given by the customer is implemented. The SDLC includes these spiral iterations practically until its finalization.
When Is It Best to Use the Spiral Model?
The Spiral Model is applied when there is a need to "learn with the product's maturity" and:
- There's a budget limit and you need to foresee risks.
- You have a medium or high-risk project to carry out.
- There is a long-term project, and changes might occur.
- The requirements are vague to the customer.
- Requirements need more clarity due to their complexity.
- The primary product has to be released in several stages to get valuable customer feedback.
- You expect major changes to the product during the SDLC.
Based on the applicability of the Spiral Model, let's view its benefits and drawbacks. The main advantage of the model is that you can add elements to the product in case they become available or known. Also, the Spiral Model involves users at the early stages of product development, which allows receiving constructive feedback.
Spiral Model Advantages and Disadvantages
4. V-shaped Model
The V-model allows a project to be carried out in a sequence and according to the V shape. The other name of this model is a Verification and Validation Model because it is based on the Waterfall Model. However, here, in the SDLC, every stage of development includes testing as well. So, you carry out a phase, complete it, test it and only then go to the next phase that will look identical to the previous one with regards to its structure.
In the V-shaped Model, the development phase corresponds to the testing phase and they go parallelly. This means you can see the Verification phases on one side of the image and the Validation phases on the other. These sides are being joined with the Coding Phase.
Based on the picture above, there are 4 Verification phases. These are:
- Requirements analysis
- System design
- Architectural design
- Module design
The validation phase also includes 4 stages:
- Unit testing
- Integration testing
- System testing
- Acceptance testing
The Coding Phase, as it is seen in the picture, combines the two other stages and makes a V shape.
The V-shaped model has the same applicability as the Waterfall Model. Requirements have to be clearly defined from the very beginning of the SDLC as going back and making changes will increase the product development costs. This model suits best for the healthcare industry.
When to Implement the V-Shaped Model?
- There are clearly defined, documented, and stable requirements.
- The technology used is also stable and the project team has a full understanding of it.
- All of the requirements are extra clear.
- The project is short-term and not complex.
The best advantage of the V-shaped Model is that you can both understand, apply to, and manage it in an SDLC easily. However, on the contrary, the model lacks flexibility when changes are on the horizon and it is quite expensive for the customer to implement those changes as they trigger additional development costs.
V-shaped Model Advantages and Disadvantages
5. Prototype Model
Prototyping is the creation of software application prototypes that show the visual representation of the minimal features of the incomplete product. This enables understanding customer requirements early in the development stage and getting valuable feedback. The model includes:
- Identification of basic requirements
- Initial prototype development
- Prototype review
- Prototype revision and enhancement
There are different types of software prototypes. These are:
- Rapid Prototyping - on understanding requirements the system is built with a clearer understanding of user needs.
- Evolutionary Prototyping - development of functional prototypes with limited functionality based on the understood requirements and adding the other requirements in the process.
- Incremental Prototyping - building numerous functional prototypes that form a system and putting them together.
- Extreme Prototyping - it is a web development domain with three phases: basic prototype in the HTML; prototype service layer; implementation and integration in the final prototype.
Where and When Is the Prototyping Model Applicable?
Prototyping is applicable to online software system development where there is a high level of user interaction. For example,
- Systems that require users to fill out forms.
- Software that requires lots of data processing.
The Prototyping Model also has its advantages and disadvantages. Of course, they depend on the organization's needs and are considered before choosing this model.
Prototyping Model Advantages and Disadvantages
6. Agile Model
Agile methodology is based on the iterative and incremental model but it is more adaptive and delivers working software at a speedy pace. Due to meeting the clients' requirements and being very flexible, the Agile methodology brings customer satisfaction. Agile projects tend to break the production process down into incremental builds or we call them iterations. Every iteration has a timeline of 1 to 3 weeks and includes different teams working on various project areas simultaneously. This allows a decrease in the time of production and it may lower production costs as well.
Every iteration consists of the same processes, which are:
- Requirements Analysis
- Unit Testing
- Acceptance Testing
At the end of every iteration, you get a working product, which is presented to the customer to understand whether the application is built according to the customer's requirements and receive feedback on the work being done.
Agile methodology is divided into several methods that have their own principles. For instance,
- Rational Unified Process (RUP)
- Extreme Programming (XP)
- Iterative Development
- Lean Software Development
When Can We Use the Agile Methodology?
- In small to medium-sized software projects.
- To produce the required multiple variants of the product.
- When you need to break down the development process into smaller parts - iterations.
- When there's a need for software delivery acceleration.
- When the team needs to be flexible in changing priorities.
- When the need is to enhance software quality, productivity, and predictability in delivery.
- To promote project risk reduction and achieve cost reduction possibilities.
- To manage the distributed teams effectively on the project.
Like any other methodology, Agile has its positive and negative aspects. For example,
Agile Model Advantages and Disadvantages
7. The DevOps Model
The DevOps model has its unique principles that promote automation and team collaboration. Therefore, the primary focus of the model is the enhancement of collaboration between teams that are driven by sequential feedback. The DevOps model resembles the Agile methodology, but differs due to the collaboration focus between technical team members and managers, while Agile focuses on client involvement.
What does DevOps carry out?
- Continuous Integration and Delivery
- Infrastructure as Code
- Monitoring and Logging
- Communication and Collaboration
When Can We Apply the DevOps Model?
- In complex projects.
- Projects that require QA and testing.
- Projects that include large teams from multiple departments.
Being quite popular, the DevOps Model also has some pros and cons. It depends on what projects you are planning to adopt this model and whether you are prepared for the quite hard adoption curve. Let's see what the model has to offer with regards to productivity from both sides.
DevOps Model Advantages and Disadvantages
Top Used Software Development Models Comparison
As the most used methodologies worldwide are DevOps, Agile (Scrum and Kanban), and Waterfall, here's a closer look at these software development models comparison.
This table with methodologies comparison shows all the distinctive features of the delivery models.
In 2020, 62% of teams evolved with the help of the DevOps model adopted to meet their company's needs. However, Agile is stepping on DevOps' feet with a 71% possibility to reduce production costs and the same number of organizations adopting it. Are Agile and DevOps friends or foes? The answer is that DevOps is Agile-driven beyond the software team.
As for the Waterfall, its success rate is equal to 26%. So, let's compare Waterfall and Agile to find out which one is better.
And again, the Agile model wins here.
How to Choose the SDLC Model That Will Suit You Best?
There is no right or wrong software development model if you approach the process of choosing one with several important steps.
Step 1: Look through all the existing software development models to understand which one is closer to your beliefs and principles as well as business needs.
Step 2: Are there any needs of Stakeholders you should listen to first? Hear out every stakeholder as they can make a difference to your final decision.
Step 3: Think about the acceptance criteria and try to answer the following questions:
- Is the model suitable for the size of the team and their skills?
- Is the model suitable for the technologies used in the project?
- Is the model suitable for both the client and the stakeholders?
- Is the model suitable for the project size and its complexity?
- Is there a project risk if we choose this model?
- Are there going to be any changes in the process of product development?
- Are the requirements fixed or flexible and may emerge during production?
Step 4: Decide which model fits your intentions.
Step 5: Optimize the model according to your project.
Now, as you have acknowledged all the project development nuances and found the model that will make a performance boost - select it and proceed with the product development.
Software engineering modeling is a good practice worldwide as it ensures the best quality of product development. Software engineering models comparison is among the most useful tools that allow choosing a methodology based on your needs. Project activities are dependent on a planned scheme and the better the team works according to this plan the better is the software processing. To choose your software model based on your internal SDLC, get to know what each model stands for, and then you will be able to define which one is the best fit. The biggest part of developers and managers in the world use DevOps, Agile (Scrum and Kanban), and Waterfall. All of these models are different according to their processes, but all they have in common is a strategic approach to product development that is successful at the output.
Published at DZone with permission of Nazar Kvartalnyi. See the original article here.
Opinions expressed by DZone contributors are their own.