Software Process Models

Software Process Models

Software process models define how software is developed. Each model offers a different approach to organizing work, managing risks, and delivering value. Choosing the right model depends on your project's size, complexity, and requirements stability.

Waterfall Model

  WATERFALL MODEL
  ===============

  Requirements    +------------------+
       ---------->|  Requirements    |
                  +------------------+
                           |
                           v
  Design          +------------------+
       ---------->|  Design          |
                  +------------------+
                           |
                           v
  Implementation  +------------------+
       ---------->|  Coding          |
                  +------------------+
                           |
                           v
  Testing         +------------------+
       ---------->|  Testing         |
                  +------------------+
                           |
                           v
  Deployment      +------------------+
       ---------->|  Deployment      |
                  +------------------+

  Each phase must complete before the next begins.
  No going back (in theory).

Best for: Projects with well-defined, stable requirements. Government contracts, safety-critical systems.

Drawbacks: Inflexible, late testing, costly changes.

Agile Model

  AGILE MODEL
  ===========

  Sprint 1        Sprint 2        Sprint 3
  +-------+       +-------+       +-------+
  | Plan  |------>| Plan  |------>| Plan  |
  | Build |       | Build |       | Build |
  | Test  |       | Test  |       | Test  |
  | Demo  |       | Demo  |       | Demo  |
  +-------+       +-------+       +-------+
       ^               ^               ^
       |               |               |
    Feedback        Feedback        Feedback

  Iterative, incremental, and adaptive.

Best for: Projects with evolving requirements, startups, product development.

Drawbacks: Requires active customer involvement, less documentation.

Spiral Model

  SPIRAL MODEL
  ============

            Risk Analysis
                |
                v
      +--------------------+
      |    Planning        |<----+
      +--------------------+     |
                |                |
                v                |
      +--------------------+     |
      |    Risk Analysis   |     |
      +--------------------+     |
                |                |
                v                |
      +--------------------+     |
      |    Engineering      |----+
      +--------------------+
                |
                v
         Customer Evaluation

  Each loop emphasizes risk analysis.

Best for: Large, complex, high-risk projects. Enterprise systems.

Drawbacks: Complex, requires risk assessment expertise, expensive.

Model Comparison

  +-------------+------------+---------+----------+
  |   Model     | Flexibility|  Cost   |  Risk    |
  +-------------+------------+---------+----------+
  | Waterfall   |    Low     | Medium  |   High   |
  | Agile       |    High    | Varies  |   Low    |
  | Spiral      |   Medium   |  High   |  Medium  |
  | V-Model     |    Low     | Medium  |  Medium  |
  | Iterative   |   Medium   | Medium  |  Medium  |
  +-------------+------------+---------+----------+

Key Takeaways

• Waterfall is linear and rigid — good for stable requirements
• Agile is iterative and flexible — good for evolving projects
• Spiral emphasizes risk management — good for complex systems
• Choose the model that fits your project, not the other way around