Due to distinct characteristics, each project would require different models to ensure objectives are met and the operation goes smoothly.
The Software Development Life Cycle (SDLC) is the process of planning, designing, creating, testing, and deploying high-quality software at the lowest possible cost and, ideally, in the shortest time. To accomplish this purpose, software engineering teams must select the best software development model for their organization’s needs, stakeholders’ expectations, and the project at hand. There are a few software development models, each with its benefits and drawbacks.
This article will run into details and compare the seven most well-known models that Project Managers (PM) can consider applying. These seven models are divided into two groups: Linear and Agile Methodologies.
Linear Methodologies are usually suitable for projects with strictly predefined requirements. The stages are fixed inflow, and each step is conducted only after the previous one is completely done.
1. Waterfall model
Waterfall methodology is one of the most traditional software development life cycle approaches. As the name implies, the method entails progressing through the linear development phases in the following order: analysis, design, development, testing, deployment, and maintenance. Each stage has well-defined tasks and milestones.
Because the Waterfall model is progressively linear, the next step cannot begin until the preceding one finishes. A stage completes when all objectives are met and a stakeholder signs off for the project to move on.
|Simple to apply|
Easy to manage and arrange tasks
Clear deliverables and milestones
|Lack of flexibility (cannot skip, backtrack, or overlap the stages)|
Costly and time-consuming because the team can only make adjustments in the maintenance stage
High risk of failure unless requirements are clearly understood
This model is perfect for:
- Simple, one-time projects with limited specifications and short deadlines
- Projects with clear, fixed requirements
- Projects that go under strict monitoring and rule compliance
Examples: Small company websites, governmental/ healthcare projects, etc.
2. V-shaped model
The V-shaped model, also known as the Verification and Validation model, evolved from Waterfall and is defined by a testing phase for each development step. Each stage, like Waterfall, begins only after the preceding one has concluded. The verification process includes 4 phases: Requirement analysis, System design, Architecture design, and Module design. In turn, corresponding to each Verification stage is one Validation step, respectively, Acceptance test design, System test design, Integration test design, and Unit test design.
|Simple & straightforward|
Early detection of errors/ problems
|Lack of flexibility (like Waterfall model)|
Difficult, expensive, and time-intensive to make adjustments
This model can be applied for:
- Mid-sized and large projects with absolutely clear objectives & requirements
- Projects where failures and recesses are not accepted
Examples: Medical software, aviation fleet management software
3. Spiral Model
The Spiral Model is primarily concerned with risk assessment. The model assembles a spiral with many loops in terms of diagrammatic presentation. Based on PMs’ risk assessment, the number of loops can be adjusted accordingly. Each loop represents a phase of the software development process divided into four quadrants: Planning, Risk Analysis, Engineering, and Assessment.
By applying this model, developers may adjust and add new features while minimizing risks via continuous and recurring development. The client reviews each phase of the cycle, which can be time-consuming for the development process due to customers’ slow response or deficient input. On the other hand, customer changes are not permitted during the engineering phase.
Precise specifications, time & budget estimation, etc
|Require highly skilled risk managers |
Costly & time-consuming
This model should be suitable for:
- Large, complex projects with unclear or too ambitious objectives
Examples: New products that need several testings, etc.
4. The Rational Unified Process (RUP)
Rational Unified Process (RUP) is an object-oriented software development procedure. The model involves four stages: Inception, Elaboration, Construction, and Transition. Except for Inception, each step is done in numerous cycles. All basic development activities (requirements, design, etc.) are carried out parallel across these four RUP phases, albeit at varying intensities.
RUP facilitates the development of both stable and flexible solutions, although it is not as rapid or adaptive as the pure Agile group (elaboration below). Depending on the project requirements, the level of client involvement, documentation intensity, and iteration time may vary.
|Complicated process and slow progress|
This model is the go-to model for:
- Large and high-risk projects, like use-case-based development and sophisticated software development
Examples: Online learning management systems
When fixed models are no longer fit for long-term projects or require higher flexibility, Agile SDLC methodology might be the one.
Agile emphasizes continuous release cycles as well as cross-functional development. It is the most adaptable and widely used SDLC model (applied by more than 70% of organizations).
The Agile approach focuses on iterative development, regular communication, and early customer feedback for improved progress.
Each iterative Agile process typically takes several weeks to build a complete software version. Instead of focusing on thorough software documentation like detailed requirement specifications or architecture descriptions, the models in this group aim to deliver the functioning part of the application quickly and evaluate it by testing activities. This enables speedy development, but because there is not a specific program description, the maintenance phase is challenging as identifying faults takes longer.
|Changeable requirements and plan|
Quick prototype release
Clear & constant communication between the development team and the clients
Continuous assessment and feedback
|Final product costs vary|
Possible conflict due to frequently changed requirements
This model is best for:
- Mid-sized projects where business requirements may not be totally converted into explicit software requirements
- Large projects that can be split into small functional sections and developed progressively throughout each iteration.
- Any project that requires end users’ early feedback
Examples: Start-up initiatives, Greenfield products (Innovative products)
The Three most popular models of Agile are Scrum, Kanban, and XP (Extreme Programming).
5. Scrum model
Scrum is implemented in short and periodic blocks called sprints, which typically last for 2 to 4 weeks and involve feedback and reflection. Each Sprint is an entity in itself, delivering a definite outcome that builds up to the final product and can be handed over to the client when required.
The process begins with objectives/ requirements that comprise the project plan. The project’s customer prioritizes these objectives based on a balance of value and cost; this is how iterations and subsequent deliveries are defined.
The lack of visible iterations is the primary differentiating aspect of Kanban SDLC. If there are iterations, they will be kept exceedingly brief, referred to as a daily sprint. The emphasis is on visualizing the plan. The team uses the Kanban board tool to display all project activities, the amount, the person responsible, and their progress. Such transparency aids in a more accurate estimation of the essential jobs.
Furthermore, the approach lacks a discrete planning step, allowing for introducing a new modification requirement at any moment. Kanban also enables the team to engage with the client regularly, allowing the customer to monitor the outcome of their work, and they may even arrange daily meetings with the project team.
The Kanban approach is employed in most software maintenance and evolution projects because of its qualities.
7. XP (Extreme Programming)
In XP, a typical repeat lasts 1-2 weeks. It also enables revisions after the iteration’s launch if the team has not previously dealt with such tools. This adaptability complicates the supply of high-quality software. XP needs pair programming, test-oriented development and test automation, continuous integration (CI), limited releases, simple software architecture, and rules combined with coding standards to solve the problem.
What SDLC model to choose for your project?
In short, based on several factors like requirements, existing organizational process, product owner involvement level or timeline, and budget, each project would need a different development model. Generally, most projects are considered to be run in Linear or Agile models. The table below summarizes the commonly used models with their objectives and functions:
|Linear models(Waterfall)||Agile models(Scrum, Kanban, XP)|
|Project objective||Enhance existing product||Develop new & innovative products (Greenfield products)|
|Requirements||Many initial requirements on product and strict regulatory conditions||Few initial requirements on development and flexible regulatory conditions|
|Product owner involvement||High||Low|
|Timeline & budget||Fixed & firm||Adjustable|
Meanwhile, Spiral and RUP models are more suitable for specific projects where risk management is the top priority. To make the best choice of SDLC model, PMs may consult IT specialists for advice based on each project’s characteristics and requirements.