Types of Software Development Models 

Introduction

The Software Development Life Cycle (SDLC) serves as a theoretical model in project management. It outlines the stages necessary for creating an information system, starting from initial business planning and ending with application maintenance.

Different SDLC models, also referred to as “Software Development Process Models”, are used during the software development phase. Each process model follows a distinct sequence of phases that corresponds to its specific nature, ensuring success throughout the software development process.

What Are Popular Software Development Models?

Currently, there are over 50 known software development models. Each has its own set of benefits and drawbacks that cater to specific software development projects or teams. While no model is without its flaws, we will delve into some of the most frequently utilised models in this field.

Waterfall Model

Once upon a time, during the dawn of programming, the sole participants of the development process were programmers. Their role was to create software functions that simplified mathematical calculations or automated other routine tasks. 

But times have changed, and today’s systems are large and complex. They necessitate the collaboration of teams with various skills, including programmers, analysts, system administrators, testers, and end-users. Together, they work towards developing software that may contain millions of lines of code.

The oldest and most popular model for developing complex software systems is the waterfall model. This model follows a multi-level development process where each stage corresponds to a specific phase of the software development life cycle, building on the previous one. Therefore, to progress to a new stage, the current one must be fully completed.

Although the waterfall model was once deemed simple, it may not always be practical in today’s rapidly evolving technological world. While a structured process may seem like an advantage at first, it can ultimately prevent the project from being completed if requirements change unexpectedly. Nevertheless, large companies with complex projects that require comprehensive risk control still rely on the waterfall model.

The benefits of the waterfall model:

• comprehensive documentation for each stage; 
• a clear plan for terms and costs;
• transparency of processes for customers. 

Drawbacks of the waterfall model:

• having to approve the full scope of system requirements at the outset; 
• the need to start over from the first stage and redo all the work if requirements change later. 

These issues can lead to increased costs and time delays.

Although the waterfall model can find some application, its dominance has significantly waned. Modern software development and methodologies have emerged, rendering it obsolete.

V-model

The V-model represents an improved version of the traditional waterfall model. Its unique feature is the meticulous monitoring of each stage to ensure a smooth progression to the next level. Unlike the waterfall model, here testing begins at the requirements stage, and each subsequent stage has its distinct test coverage level.

A unique aspect of the V-model is that a separate test plan is developed for each testing level. This approach enables the team to formulate a testing strategy for the subsequent level while testing the current level. Additionally, the expected test results are defined, and entry and exit criteria for each stage are determined when creating test plans.

Advantages of the V-model:

• strict staging;
• early test planning and system verification;
• intermediate testing;
• improved time management compared to the waterfall model.

Drawbacks of the V-model:

• insufficient flexibility;
• it does not accommodate dynamic changes;
• the actual creation of the program takes place during the code writing stage, which is already in the middle of the development process;
• risk analysis may be insufficient;
• it does not account for different work happening in parallel.

Iterative and Incremental Model

Not all software development models follow a linear sequence of actions. The iterative, or incremental, models take a different approach by breaking down the product life cycle into a series of mini-cycles, each with the same basic stages as traditional models in software development. These mini-cycles are called iterations, and in each iteration, a separate component of the system is developed and then added to the previously developed functionality.

Unlike traditional software development models, the iterative model does not require a complete set of requirements to begin work on the product. Instead, development can start with requirements for a portion of the functionality, which can be added and modified in subsequent iterations. With each iteration, a new version of the product is created, ensuring that it meets the evolving requirements of the project.

The iterative model is composed of four main stages, which are repeated in each iteration (plan-do-check-act):

1. Definition and analysis of requirements;
2. Design and engineering – based on the requirements, design can be developed either separately or added to an existing one;
3. Development and testing – coding, integration, and testing of a new component;
4. Review phase – assessment, revision of current requirements, and proposals for additions.

Based on the results of each iteration, a decision is made on whether its results will be used to supplement existing functionality as an entry point for the next iteration (also known as incremental prototyping). Ultimately, when all the requirements have been met, the product is ready for release.

In mathematical terms, the iterative model represents the implementation of successive approximation, which is a gradual approximation to the image of the finished product.

The key to the success of this model is the strict verification of requirements and thorough validation of the developed functionality in each iteration. The main stages of the iterative model closely resemble those of the waterfall model, as each iteration creates software that requires testing at all levels.

Advantages of the iterative model:

• the early creation of working software, which can be improved in subsequent iterations;
• flexibility;
• easier testing and risk analysis for each iteration.

Drawbacks to the iterative model:

• each phase is independent, and individual iterations do not overlap;
• possible problems with the overall architecture of the system, since not all requirements are known at the beginning of the design process.

Spiral Model

The spiral model is a unique software development process that incorporates aspects of both iterative and waterfall models. The model consists of four sectors, each representing distinct stages of the development process: goal setting, risk assessment, development and testing, and planning for the next iteration.

The product’s life cycle in the spiral model is depicted as a spiral that unwinds with each subsequent step, starting at the planning stage. At the end of each iteration, a tested prototype that complements the existing build is expected to be delivered. The goal is to develop a prototype that meets all the requirements and is ready for release.

The spiral model is characterised by its focus on identifying and managing potential risks, with a specific stage dedicated to evaluating them. 

Common risks that may arise during software development:

• unrealistic budgets and deadlines;
• lack of expertise;
• frequent requirement changes;
• over-optimisation;
• low system performance;
• inconsistent qualifications among team members.

Advantages of the spiral model:

• improved risk analysis;
• well-documented development process;
• flexibility;
• early creation of working prototypes.

Drawbacks of the spiral model:

• potential expenses;
• effective risk management requires highly qualified specialists;
• the success of the process largely depends on the risk analysis stage;
• may not be suitable for small-scale projects.

Scrum

The term “Scrum” originated from rugby, where it described the position of the teams at the beginning of the match before the game begins. In software development, Scrum methodology is valuable for its minimal resource requirements and the set of common rules that enable effective teamwork. It is a process of creating a product with high-priority business opportunities, achieved through a series of fixed time intervals known as sprints.

Before each sprint, a meeting is held to plan tasks and the sprint duration. At the end of each sprint, a review session is held. That’s when the customer is presented with a version of the product that includes all the functions implemented during the latest sprint. The customer must then accept the product or request adjustments, which will determine the next step, whether it is another sprint or the delivery of a finished solution.

Sprint duration ranges from 1-4 weeks. It’s determined based on the type of product and the tasks at hand. Shorter sprints allow for faster development, greater flexibility, and more opportunities for customer feedback. Longer sprints, however, reduce overhead costs associated with meetings and corrections.

Scrum is a popular methodology that can be very effective in certain situations. However, to use Scrum effectively, several conditions must be met:

• If the problem is complex, difficult to predict, or requires experimentation and research to find the best solution, then Scrum is very useful. If the solution depends on a clear algorithm, then Scrum may not be the best choice;
• If the cost of error is high, Scrum may not be appropriate;
• The system requires feedback and customer involvement to function effectively;
• The team needs to be well-qualified and have sufficient budget and resources to achieve maximum efficiency in a short time period;
• If the methods used don’t allow for experimentation and testing, the system may be ineffective;
• If there are communication issues within the team or too much bureaucracy, the Scrum methodology may not be effective.

Despite these limitations, Scrum has many benefits:

• It allows teams to solve complex problems quickly and creatively. This means you can find not just an acceptable, but the best course of action to any given issue;
• Team self-organisation removes the need for intermediaries and allows developers to respond to changes quickly;
• Scrum reduces development time.

Scrum motivates the team to work efficiently and eliminates the risk of “passive sabotage” that can slow down the development process.

Extreme Programming

Extreme Programming, also known as XP, is a popular agile software development methodology that has its own set of processes, tools, and roles. While XP’s creator didn’t invent anything entirely new, they refined and enhanced the best practices of flexible development, making it the “extreme” programming it is today. 

XP’s goal is to handle the constantly evolving requirements of software products while simultaneously enhancing development quality. As a result, XP is well-suited for intricate projects with a lot of uncertainties.

The XP methodology revolves around four critical processes: coding, testing, design, and listening. XP also emphasises five core values: simplicity, communication, feedback, courage, and respect. 

The advantages of XP can only be seen when a team fully embraces at least one of the XP practices. If you’re considering giving it a go, there are several compelling reasons to do so: 

• XP can ensure that customers receive precisely the product they need, even if they have only a vague idea of what the final product should look like; 
• The team can make changes to the code and add new functionality quickly through simple code design, frequent planning, and releases; 
• By continuously testing and integrating scripts, XP produces high-quality standardised code that is easy to maintain;
• XP also provides a fast pace of development through pair programming, minimal revisions, and customer involvement in the development process;
• This method can reduce the risks associated with development by distributing responsibility evenly among team members, thereby ensuring that the layoff or hiring of a team member will not derail the project;
• Moreover, the costs of development can be lowered since teams can focus on coding rather than documentation and collections.

Despite its advantages, XP has sparked some controversy and received criticism from teams that have struggled to implement it successfully. It’s worth noting that it has its weaknesses. 

• The success of XP depends heavily on customer involvement, which can be difficult to achieve;
• It’s challenging to predict the time needed for a project because requirements may not be fully known at the beginning;
• XP is best suited for senior specialists since the methodology is highly dependent on their expertise;
• Management may be hesitant to adopt pair programming due to a perceived increase in cost;
• Regular meetings with programmers can be expensive for customers;
• Cultural change is required to implement XP effectively, which may be stressful for management and clients;
• The lack of structure and documentation in XP may also make it unsuitable for large projects;
• Non-functional quality requirements for products can be difficult to describe using user stories since flexible methodologies tend to be function-oriented.

Kanban

Kanban is a well-known Agile approach that facilitates effective goal setting and workflow organisation to accomplish desired outcomes. This methodology emphasises transparency in terms of work progress and enables businesses to visualise the entire workflow.

Kanban allows for efficient tracking of task progress and workload distribution among employees, enabling effective team management and project implementation monitoring. Its visualisation feature ensures that every team member is fully informed of the current progress. Let us delve into the fundamental principles of the Kanban methodology.

• Visualisation of processes. This is a critical aspect, where all assigned tasks should be added to the plan, with status updates provided as each completed stage is reached. This strategy aids in incremental progress monitoring and identification of time-consuming tasks that require additional support.
• Task grouping. Task groups are determined by their status, with the three most commonly used columns being “To be done”, “In progress”, and “Done”. This method involves the transfer of tasks from one stage to another and simplifies the visualisation of the workflow.
• Attention to unfinished tasks. Businesses need to understand the underlying reasons for task delays, provide additional resources or support, and motivate employees to complete the work.
• Continuous improvement. This is achievable by monitoring task deadlines and progress in the Kanban system to identify weak points in processes. This approach assists businesses in determining areas that require more or less attention and adjusting the workload accordingly.

The Kanban methodology is a versatile approach that can be employed in diverse fields, from HR recruitment to software development, startups, and even blogging. This method is also useful in customer relationship management (CRM) systems for developing sales pipelines. Let us explore the benefits of this methodology.

• Planning flexibility. The team can focus on a specific task while the manager can modify the priority of various tasks without impacting the overall workflow. Once a task is completed, the team can then move on to the next task.
• Deadline tracking. Kanban improves control of deadlines by facilitating the tracking of workflow progress, optimisation of workflow duration, and prediction of the time needed to solve future tasks.
• Enhancing work efficiency. Kanban improves efficiency by minimising multitasking, which can reduce work quality and slow down progress. The Kanban system reduces stagnation by quickly identifying weaknesses, which improves task completion time and results in better quality outcomes.
• Visibility of work progress. This is one of the major benefits of Kanban process management. With all team members having access to assigned tasks and progress performance, it is easier to identify issues and take appropriate actions to resolve them.

Having explored the advantages of the Kanban methodology, it is now imperative to consider its drawbacks.

• Firstly, the Kanban method is not suitable for long-term planning. It is designed to achieve short-term goals, and the focus is on addressing immediate issues. Task priorities may also change depending on circumstances, which may impact the long-term planning of the work process.
• Secondly, the Kanban approach may not be suitable for large teams. The more people involved in the work process, the harder it is to manage and control the execution of tasks. Thus, it is recommended to have no more than ten people in a team, with ideally five being the optimum number.

The Rational Unified Process

The Rational Unified Process (RUP) is a widely applicable methodology for assigning tasks and responsibilities during software development. Its primary aim is to produce software that meets the needs and demands of users while maintaining high quality. RUP was created by Rational Software Corporation, which was acquired by IBM in 2003.

The resounding success of the RUP approach has made it clear to numerous companies that having a well-defined and documented development process is crucial. However, because RUP is designed for large development projects, many managers believe it is unsuitable for small tasks that do not necessitate a significant amount of resources. Nonetheless, several examples demonstrate how small projects have greatly benefited from implementing RUP.

Here are the principles of the RUP methodology:

• Iterative development model. This principle involves identifying and eliminating risks at every stage of the project to gain a better understanding of the problem and to make changes until an acceptable solution is found.
• Requirements management. RUP provides a framework for organising and tracking functional requirements, documentation, and selecting optimal solutions for both the development process and the business.
• Component architecture. The RUP methodology breaks down the system architecture into components that can be used in current and future projects.
• Visual modelling of software. This principle implies creating a visual model of a piece of software to understand the structure and behaviour of its architecture and components.
• Software quality control. The RUP methodology ensures quality control of all team actions during the software development process.
• Change control. This principle involves tracking changes to build a continuous development process and create a favourable environment in which the team is protected from radical workflow shifts.

RUP benefits:

• The RUP methodology allows developers to handle changes in requirements more effectively, whether they originate from the client or emerge during the project’s implementation.
• RUP places significant importance on having precise documentation at every stage of the development process.
• RUP emphasises requirements integration throughout the whole software development process, especially during the build phase.

RUP disadvantages:

• RUP requires experts and professionals to assign tasks to specific workers, which can limit autonomy and creativity among team members.
• Integration of RUP into the development process may have a negative impact on other critical activities, particularly during  phases of the testing.
• Despite its effectiveness in software development, RUP is a complex methodology that can be challenging to implement, especially for small teams or companies.

Conclusion

Selecting the appropriate software development model is a crucial step in software product development. The models provide clear guidance and solutions to challenges you may encounter during the process, making it easier to achieve the desired outcome. 

With the top software development methods outlined above, you can confidently tackle your project regardless of complexity. However, if you prefer to entrust your future solution to a custom software development company, make sure the vendor is well-versed in different approaches to software development.

And while you’re at it, consider Bamboo Agile as your partner. Our expertise has been recognised by many well-known brands in various industries, including e-Commerce, Education, and Telecom. Contact us now to schedule a free consultation with our specialists, and take the first step towards success.