Introduction
The incremental model is a foundational concept in software engineering and systems development. It is a software development methodology in which software requirements are broken down into multiple standalone modules.
It is a software development life cycle (SDLC) model that blends waterfall and iterative approaches. Unlike traditional systems that offer the entire product at once, the incremental model delivers the software in smaller, more manageable chunks known as “increments.” This approach enables early partial implementation, making it easier to manage risks, handle modifications, and collect user feedback throughout the development cycle.
The Project Management Institute defines an incremental approach as an “adaptive development approach in which the deliverable is produced successively, adding functionality until the deliverable contains the necessary and sufficient capability to be considered complete.” Using this module, we can add full 100% capability to our system with no small errors.
In the incremental model, each step will be prioritized, but the most important aspect of the product will be addressed first. It is possible to delegate tasks to development teams because they are broken down into discrete modules. The iteration will not end till the final product is complete. According to the incremental model, the given early increment should have functionality that is of interest to the client.
Characteristics of the Incremental Model
- Incremental Development: The product is designed, built, and shipped in stages. Each piece (or increment) increases functionality.
- Progressive Build-up: Increments can be scheduled so that each succeeding release adds functionality or improves on the current system.
- User comments: Users can interact with early versions and contribute comments, which will affect future updates.
- Flexibility: Changes are easier to incorporate in subsequent increments without affecting the entire system.
- Parallel Development: Different components can be created concurrently in distinct teams and then combined.
Development phases of the incremental model
Requirement analysis
The Requirement Analysis step serves as the Incremental Model’s foundation. This phase involves gathering system requirements from stakeholders and end users. Unlike the Waterfall model, which finalizes all requirements at once, the incremental model allows for partial requirement gathering, with only the fundamental requirements for the initial increment fully established. This enables early product release and iterative revision based on user feedback.
Requirements are prioritized, with key features reserved for early increments and less critical functions for later stages. This flexibility ensures that the most valuable components are given first. Importantly, any ambiguities or gaps can be rectified in subsequent increments, making this paradigm ideal for projects in which total requirement awareness is not achievable from the start.
System design
During the System Design phase, the development team converts the assessed requirements into a structured roadmap for development. This phase consists of two main components: high-level architectural design and detailed design for each increment. The high-level design describes the overall system architecture, the technologies to be employed, data flow diagrams, and how each increment will fit into the larger system.
For each increment, a thorough design is generated to specify internal module interactions, database schema (if applicable), user interface structure, and component dependencies.
This phase is iterative and adaptable. As requirements increase in successive increments, the design must stay adaptable enough to accommodate modifications without compromising existing functionality. UML diagrams, system flowcharts, and ER models are popular tools for visually representing system components.
Implementation
The Implementation phase is where actual coding occurs, converting plans into executable software. The Incremental Model divides implementation into modules or increments, each of which provides a piece of the system’s overall capability. The first increment includes the system’s essential features, whereas succeeding increments add new features or improve current ones.
Each increment has its own mini-software development lifecycle, which includes coding, unit testing, and integrating with prior increments. Developers prioritize modularity, ensuring that new code adheres to the architecture established during the design phase. Version control systems and continuous integration tools are useful for managing changes and dependencies between increments.
Testing
In the Testing phase, each increment is rigorously evaluated to ensure that functionality, integration, and performance meet requirements. This phase comprises both individual module testing (unit tests) and incremental integration testing to ensure that newly built components interact seamlessly with previously finished sections of the system.
Testing for each increment begins as soon as the implementation is completed. Test cases are based on the requirements for that increment. Developers and QA teams do black-box, white-box, and regression testing. Automation technologies can be used to accelerate the testing process, especially for repetitive or regression tests.
During this phase, testers and users provide feedback that guides adjustments for current and future increments.
When to use an incremental model?
The Incremental Model is particularly suitable in scenarios when:
- Requirements are well understood: When the fundamental requirements are clear, additional functionality can be added over time.
- Early Product Release is Desired: When stakeholders need a functional product early in the development cycle.
- High-risk features are involved. enables early testing and validation of high-risk components.
- Limited Resources Available: Allows for staggered resource allocation, lowering initial investment.
- Projects with Long Development Schedules: Enables manageable development over extended periods.
Advantages and Disadvantages
Advantages
- Risks are identified and addressed in each increment, which reduces the likelihood of project failure.
- Smaller increments allow for more manageable testing and easier debugging of difficulties.
- Continuous delivery allows for continual user input, which can improve the overall quality and relevancy of the product.
- Because only a fraction of the program is originally produced, investments can be spread out over time.
- Resources can be allocated and changed as needed for each increment, resulting in increased team efficiency.
- Functional software can be delivered early, delivering value to users even before the entire system is built.
- Regular releases make it easy for stakeholders to monitor progress and evaluate project health.
- The system can evolve, introducing new features as the user base or business expands.
- Multiple teams can work on various increments concurrently, accelerating overall development.
- Problems are easier to identify and resolve since they are isolated in smaller increments.
- Clients observe progress regularly and feel more involved in the growth process, which increases satisfaction.
- Code and components created in previous phases can frequently be reused in later levels.
- As technology advances during the development process, newer increments can incorporate updated tools or methodologies.
Disadvantages
- Integrating each increment into the existing system can get hard over time.
- Each increment must be carefully considered to assure compatibility and overall consistency.
- The cost of recurrent development cycles, testing, and integration may be more than in other models.
- Users may initially have access to only the most basic functions, which may not meet all of their requirements.
- As more modules are introduced, it becomes more difficult to manage their dependencies.
- Continuous user interaction and feedback might result in increased scope and feature bloat.
- The initial design must be strong and expandable to accommodate future increases, which needs foresight and competence.
- The full system capability is not available until the last increment is provided.
- Users may require ongoing training or documentation updates as new features are introduced on a regular basis.
- Integrating each increment into the existing system can get hard over time.
- Each increment must be carefully considered to assure compatibility and overall consistency.
- The cost of recurrent development cycles, testing, and integration may be more than in other models.
- Users may initially have access to only the most basic functions, which may not meet all of their requirements.
- As more modules are introduced, it becomes more difficult to manage their dependencies.
- Continuous user interaction and feedback might result in increased scope and feature bloat.
- The initial design must be strong and expandable to accommodate future increases, which needs foresight and competence.
- The full system capability is not available until the last increment is provided.
- Users may require ongoing training or documentation updates as new features are introduced regularly.