Incremental Process Model - Software Engineering

The Incremental model is a software Development approach which is used to breakdown the project into smaller and easily manageable parts. In these, each part passes through Requirement, Design, Testing phases and Implementation phase. The overall process continue until we got the complete System.

Incremental Process Model

The Incremental Process Model is a method of software development where the system is built step by step. Instead of delivering the whole system at once, it is developed and delivered in small parts called increments. Each increment builds upon the previous one by adding new functionality, until the complete system is finished.

Key Characteristics of Incremental Process Model

• Partial System Delivery: The system is developed and delivered in small, manageable pieces. Each part adds new features to the previous version.
• Early Functionality: Basic functionality is available early in the project. This allows users to start using and testing the system quickly.
• Customer Feedback Loop: Feedback is collected after each part is delivered. This helps improve the next version of the system.
• Flexible to Changes: Changes or new features can be added between increments. This makes the model flexible to evolving needs.
• Combination of Linear and Iterative Approaches: Combines the structured approach of Waterfall with flexibility. Supports both planning and ongoing improvements.

Phases of the Incremental Model

The phases of Incremental model is divided into the four parts which is Requirement, Design, Testing phases and Implementation phase. In those phase, the process continues until we got the expected output at the end.

Requirement Analysis

The first step in the Incremental Model is understanding what the software needs to do. The team gathers the requirements from the product experts and clearly defines the system’s functional needs. This phase is important because it sets the foundation for everything else in the development process.

Design & Development

Next, the team focuses on designing how the software will function and starts developing it. They work on adding new features and making sure the system works as expected. The design and development steps go hand-in-hand to build the functionality of the software.

Testing

Once a feature is developed, it goes through testing. The testing phase checks how the software performs, including both new and existing features. The team uses different testing methods to make sure everything is working correctly.

Implementation

This phase involves writing the final code based on the design and development steps. After testing the functionality, the team verify that everything is working as planned. By the end of this phase, the product is gradually improved and updated until it becomes the final working version.

Types of Incremental Model

The Incremental Model has two main types, each offers different approaches to how software is developed in parts. Here are the two types:

Staged Delivery Model

The Staged Delivery Model develops software in a sequence of planned stages, where each stage delivers a functional part of the system. Each release brings the product closer to completion, allowing it to evolve gradually. Working versions are delivered at regular intervals, making progress visible and manageable throughout the development process. The diagram below shows this model :

Parallel Development Model

The Parallel Development Model divides the system into multiple modules that are developed simultaneously at the same time by different teams. By working on separate components in parallel, the development process becomes faster and more efficient. This approach reduces overall project time and allows teams to focus on specific functionalities concurrently. Given below is the diagram showing the model:

Use Cases of Incremental Process Model

• When the requirements are well-defined and clear
  Because increments can be planned and developed step-by-step with minimal requirement changes.
• If the project has a long development timeline
  Incremental delivery helps manage complexity over time by breaking the project into smaller, manageable parts.
• If the customer needs a quick product release
  You can deliver the most critical features early in the first increment, allowing the customer to start using the software sooner.
• When you want to develop the most important features first
  This allows early feedback on key functionalities and better prioritization for subsequent increments.

Note: The Model is not ideal when the software development team is not highly skilled or experienced because managing increments and integrating them well requires a competent team.

Advantages of Incremental Process Model

The Incremental Model of software development builds a system in small, manageable sections (increments), making it a good choice for many projects. Below are the key advantages:

• Faster Software Delivery
  • Initial working versions of the software can be delivered quickly.
  • Early delivery increases customer satisfaction and feedback opportunities.

• Clear Understanding for Clients
  • Clients get to see parts of the system at each stage.
  • This visibility ensures that the final product meets their expectations.

• Easy to Implement Changes
  • Requirements can evolve, and changes can be incorporated in subsequent increments.
  • It supports flexibility without heavily disrupting earlier stages.

• Effective Risk Management
  • Risks can be identified and handled early due to the staged approach.
  • Each increment allows for testing and validation, reducing the impact of unforeseen issues.

• Flexible Criteria and Scope
  • Requirements can be adjusted without a major cost increase.
  • Better scope management helps keep the project aligned with business goals.

• Cost-Effective
  • Compared to models like the Waterfall, the incremental model is generally more cost-efficient.
  • Budget is spread across stages, making it easier to manage finances.

• Simpler Error Identification
  • Since development is done in parts, it's easier to pinpoint and fix errors within a specific increment.
  • Testing each module separately enhances quality and reliability.

Disadvantages of Incremental Process Model

Incremental Model comes with some limitations and challenges. Below are the key disadvantages:

• Requires a Skilled Team and Proper Planning
  • Successful implementation demands an experienced team.
  • Poor planning or coordination can lead to confusion between increments.

• Cost Can Increase Over Time
  • Due to repeated testing, redesign, and integration in every cycle, the overall project cost may rise.
  • Continuous iteration involves added overhead

• Incomplete Requirement Gathering Can Cause Design Issues
  • If all requirements are not identified early, the system architecture may not support future needs.
  • Inadequate upfront design can lead to rework and architectural mismatches.

• Lack of Smooth Flow Between Increments
  • Each iteration may function independently, which can create inconsistencies.
  • There might be integration challenges when combining all the increments into a unified product.

• High Effort to Fix Repeated Issues
  • A defect in one increment may exist in others.
  • Fixing the same issue across multiple units can be time-consuming and resource-intensive.

For more understanding of different models, you can refer to SDLC.