Choosing the right software development model directly affects how the program will work. Therefore, in this article, we want to explain different types of software,  еxplorе how they work,  find out how thе choice of a particular model affеcts thе project,  and givе you specific advice on how to choosе the right approach for your projеct.

What are software development models?

Softwarе dеvеlopmеnt modеls arе rulеs or a systеm of rulеs that spеcify in what ordеr to perform various stеps and how to carry out thе procеss of crеating a program.  Each type of SDLC modеl has its features that arе usеd during dеvеlopmеnt.

The main purpose of the software engineering models is:

• to help developers and development teams establish a sequence of actions;
• define the roles and responsibilities of the process participants;
• mark important milestones and ensure the high quality of the finished software product.

The choice of a particular model may depend on the project requirements, type of work, and development team, and therefore, it is important to carefully consider the various options before starting to develop a software product.

Types of models in software engineering

There are the following  types of SDLC models:

• Waterfall
• V-model
• Incremental and iterative models
• Spiral
• RUP
• Agile model

1. Waterfall:

This classic model was used in the early days of development and continues to be actively used today. Its working principle is simple: each subsequent stage is performed only when the previous one is completely finished.

This type is rather rigid and has strict rules. It clearly defines the terms of each stage. But there is a disadvantage: it is very difficult to take a step back. Making corrections to an existing project is very expensive and problematic.

This method is suitable only for projects that are clearly outlined, there is a full understanding of what is being created, for what purposes, and what requirements are set.

Advantages:

• Development is easy to control. The customer always knows what the programmers are doing now and can control the timing and cost.
• With this type of software engineering model, the cost of the project is determined at the initial stage. All steps are planned already at the stage of contract approval, software is written continuously «from and to».
• There is no need to hire testers with a serious technical background. Testers will be able to rely on detailed technical documentation.

Disadvantages:

• Testing starts at the last stages of development. If a mistake has been made in the product requirements, fixing it will be expensive. Testers will discover it when the developer has already written the code and technical writers have already written the documentation.
• The customer already sees the end product and only then can give feedback.. There is a high probability that they will not be satisfied with the result.
• Developers write a lot of technical documentation, which delays the work. The more extensive the project documentation is, the more changes need to be made, and the longer it takes to coordinate them.

2. V-model:

A type of design model in software engineering where each development phase has a corresponding testing phase.

The V-shaped model is suitable for systems that have a particular need for uninterrupted operation. For example, applications in clinics for patient monitoring, integrated software for vehicle airbag control mechanisms, etc.

A feature of the model can be considered to be that it is aimed at thoroughly checking and testing a product already at the initial stages of design. The testing stage takes place at the same time as the corresponding development stage, e.g., unit tests are written during coding.

Advantages:

• The number of errors in software architecture is minimized.

Disadvantages:

• If an error is made during architecture development, it will be expensive to go back and fix it, just like in the «waterfall» model.

3. Incremental and iterative models in software engineering:

The incremental software development model is suitable if the project has a clear action plan, but the product needs to be launched quickly, and changes can be made later.

Its essence is that first, a set of tasks is worked out, and they are prioritized. Then, each «block» is developed according to the traditional cascade model.

• Initially, a «basic» product with minimal but important functions is made.
• It is gradually supplemented by developing other components, which are called increments.
• The process is looped until there is a fully assembled single system.

The essence of iterative software development methodology is to create and gradually improve a basic functionality. While it sounds similar to the previous option, there is a difference.

The incremental software process model in software engineering can be compared to a jigsaw puzzle where all the elements are laid out step by step and gradually assembled into a single picture.

Advantages of the incremental model:

• You do not need to invest a lot of money at the initial stage. The customer pays for the creation of basic functions, receives the product, «rolls» it out on the market, and decides whether to continue development based on the results of feedback.
• You can quickly get feedback from users and promptly update the terms of reference. This reduces the risk of creating a product that no one wants.
• A mistake is cheaper. If an error is made while developing the architecture, it will cost less to fix it than in the «waterfall» or V-model.

Disadvantages of the incremental model:

• Each team of programmers develops its own functionality and can implement the product interface in its own way. To prevent this from happening, it is important at the stage of discussing the technical task to explain what it will be like so that all project participants have a common understanding.
• Developers will postpone the finalization of the main functionality and «see the little things». To prevent this from happening, the project manager should control what each team is doing.

Advantages of the iterative model:

• Quick release of a minimal product gives you the opportunity to get feedback from the customer and users quickly. This means that you can focus on the most important software features and improve them in accordance with market requirements and customer's wishes.
• Constant testing by users allows you to detect and eliminate errors quickly.

Disadvantages of the iterative model:

• Using databases or servers at the initial stage - the former are difficult to scale, and the latter cannot handle the load. You may have to rewrite much of the application.
• Lack of fixed budget and deadlines. The customer does not know the end goal and when the development will be finished.

4. Spiral modеl:

A model that combines quantitative and cyclical development methods. Spiral models of software development are suitable for large projects where mistakes can lead to significant losses or unpredictable consequences. Emphasis is placed on risk assessment and working out specific business tasks. The principle of work is as follows:

The work follows a spiral, at each turn of which there are 4 main activities

1) Creating a plan;

2) Risk analysis;

3) Development and design;

4) Evaluating the result and collecting feedback.

If all 4 stages are successfully completed, the development moves to a new spiral.

Benefits:

• Great attention is paid to risk elaboration.

Disadvantages:

• There is a risk of getting stuck at the initial stage - endlessly improving the product's first version and not progressing to the next one.
• Development takes a long time and is expensive.

5. Rational unified process:

Rational Unified Process (RUP) is an Agile software development methodology. The RUP life cycle consists of four phases: start, develop, design, and transfer. Each of the phases has mandatory goals. Moreover, developers can iterate further as needed until requirements are met. A full-fledged software development consists of 10-15 iterations on average.

Benefits:

• RUP methodology allows you to deal with changes in requirements, whether they come from the client or arise during the course of the project.
• RUP emphasizes the need for accurate documentation.
• Requirements integration occurs throughout the development process, and in particular in the build phase.

Disadvantages:

• RUP relies on the ability of experts and professionals to assign actions to certain workers, who are then required to produce the planned results in the form of artifacts.
• Integration into the development process can negatively impact other more fundamental activities in the testing phases.

6. Agile model in software engineering:

Agile software development methodology is a methodology based on an iterative method in which conditions and solutions evolve through the mutual work of self-organizing cross-functional teams.

Benefits:

• Early stage testing.
• Ability to evaluate added functionality «in action».
• User experience research at all stages.
• Ability to quickly present a «raw» but working version to the market.

Disadvantages:

• Lack of a clear project development plan.
• Constant threat of redoing a large part of the work.
• Reduction of product quality in favor of speed and simplification.

Through Agile types of SDLC, it is possible to make the project management process more streamlined.

Such projects involve learning adaptation processes, teamwork, self-organization, reporting, and audits.

Agile methods are considered to be cutting-edge in design. Their purpose is to produce high-quality software quickly.

These methods include:

a) Extreme Programming (XP):

XP differs from other Agile methodologies in that it only applies to software development. It cannot be used in other businesses or everyday life like Scrum or Kanban.

The XP methodology aims to cope with the ever-changing requirements of a software product and improve the quality of development. Therefore, XP is well-suited for complex and uncertain projects.

The XP methodology builds around four processes: coding, testing, design, and listening. In addition, Extreme Programming has values: simplicity, communication, feedback, courage, and respect.

b) Scrum:

Scrum is an Agile methodology by which teams can structure work through short development cycles called sprints. Scrum teams commit to delivering results at the end of each sprint and implement practices and team structures that help them achieve this frequency. Scrum takes this further by providing a structure to help teams apply Agile principles to their day-to-day work.

c) Kanban:

Kanban is an Agile methodology that helps teams continuously deliver results. Kanban teams organize their work on a Kanban board using cards, columns, work-in-progress limits, specific commitments, and delivery points.

The Kanban methodology is ideal for knowledge-building work where the product or service is fairly invisible. Kanban helps teams visualize achievements and make progress day in and day out.

Differences between Scrum and Kanban software development process models

Scrum and Kanban are often compared, but the comparison doesn't always make sense - they don't compete or exclude each other. Scrum helps to solve a large complex task, while Kanban helps to optimize the workflow.

What are the best software development models?

The best models of software development depend on what your project requires. You can choose the suitable model for you in the following steps.

Steps to select the different software development models:

• Understand the project requirements
• Assess the risks
• Consider resources and timelines to choose models of software development
• Compare and choose
• Adapt and monitor

Step 1: Understand the project requirements

Understanding the project's nature, timing, and constraints will be essential to choosing the suitable software development process models.

• First, it is necessary to explore the idea. It is crucial to understand how you see your future product. This allows the idea to be formed and its prospects to be assessed.
• Then, you need to study competitors, similar products on the market, target audience, and opportunities and conduct a number of analytical studies to understand how to turn the idea into a working product.

Stеp 2: Assess the risks

Every project has risks. In this case, however, the risks are so serious that it is not known in advance whether the system can be realized. If there are such risks, you will probably start development with prototypes, concepts, models, etc., to determine whether it is fundamentally possible. In this case, the spiral model is the best model for you.

If there are no such risks in your case, the next question is whether the requirements will change. If they are well known in advance, and you are sure the customer will not make any significant changes during the development process, then you should choose the Waterfall development model.

We recommend choosing it when the project has a short duration. In case of clear and unchanging requirements together with a short period, the Waterfall model, compared to the iterative model, will give less overhead on the process.

At the implementation stage, programmers will not be distracted from writing code: neither the need to urgently fix bugs from the previous iteration nor endless rallies and releases.

Stеp 3: Consider resources and timeline to choose models of software development

Next, evaluate your project timeframe to determine which development method is most effective for your project. Of course, the projected duration of your software development project strongly influences the choice of methodology.

For example, you may want to explore the Waterfall methodology for long-term development with no looming deadlines. Here, your team can complete each phase before starting the next.

On the other hand, for projects that go through sprints and quickly approaching deadlines, consider iterative models. This way, you have the option to release partially finished products if needed.

Of course, evaluate your timeline to help you choose the best development methodology.

Stеp 4: Compare and choose

Finally, based on your software development factors, you can choose your methodology. Choose the model that best fits the requirements of your project. Usually, there is no one «best» of the various software development models, but it is the one that works best in your particular situation. Or you can mix and match aspects of the framework to create your own methodology.

Stеp 5: Adapt and monitor

Remember that selecting a method is only the first step. Adapting different models in software engineering to your needs and regulating the development process is critical to a good outcome.

Main stages of software development

1. Defining the strategy
2. Analyzing
3. Design
4. Realization
5. Testing
6. Implementation
7. Usage and technical support

No matter which of the different types of software engineering models you have chosen, the process will still follow typical development stages. The stages may change slightly depending on the chosen method; other approaches are used, but the principle remains the same. Software development goes through the following stages:

1. Defining the strategy

Finding out the requirements, assessing the realization of these requirements, calculating the budget, and determining the possibility of performing the work for the client on mutual terms. This stage may occur only once in the cycle.

2. Analyzing

Investigating the functions defined in the strategy phase, attributes, and relationships. This stage usually occurs immediately after the strategy is defined and may be repeated in a cycle.

3. Design

Gathering the data model.

4. Realization

Developing the product according to the requirements and the whole team's interaction to achieve the final goal is one of the most intense phases of the development cycle.

5. Testing

This phase can run in parallel with the realization phase. Testing of everything that developers do, the work of the product.

6. Implementation

Often, the product is implemented in iterations to do it better, gradually dealing with bugs and difficulties. During the implementation phase, your main tester will be your client. The entire system goes to full capacity and starts working for its users.

7. Usage and technical support

Keeping the project afloat, interacting with the client, users, etc. It all depends on the conditions of working on the project.

Summary about software engineering models

We have introduced you to the different models of software development. It is impossible to say which of them will suit your project better. You have to choose the best one on your own, based on the project's objectives, budget, team, and deadlines. Many of them overlap with each other. You may have to try several of them before you find the one that will lead your project to success and make your work more productive.