Study sheet: SDLC Models

📋 Course Outline

1. SDLC Definition and Purpose
2. SDLC Phases and Categories
3. Waterfall Model
4. V-Model Verification and Validation
5. Incremental Model
6. Iterative Model
7. Rapid Application Development

📖 1. SDLC Definition and Purpose

🔑 Key Concepts & Definitions

• Software Development Life Cycle : A well-structured process that guides software development projects from inception to retirement and describes the typical phases and progression between phases.

★ Must-know

• The purposes of the SDLC are to deliver reliable and functional software, avoid common pitfalls, and keep projects on schedule.

Further detail

• The SDLC is also known as software development models, software development process models, or software development methodologies.

• The SDLC ensures systematic development, quality standards, risk reduction, resource optimization, and alignment with business goals within a reasonable timeframe.

💡 Memory Hook

Picture the SDLC as a living organism progressing from inception to retirement.

📖 2. SDLC Phases and Categories

★ Must-know

• A common SDLC model contains seven phases:

  • Planning
  • Analysis
  • Design
  • Coding or implementation
  • Testing
  • Deployment
  • Maintenance

• Planning defines goals, scope, cost estimates, feasibility studies, and timelines, while analysis defines requirements with developers, subject-matter experts, customers, and end-users.

• Testing verifies functionality and performance through unit, integration, system, and acceptance tests, deployment moves the application into production, and maintenance provides support, updates, and feature enhancements.

📌 Predictive models complete phases sequentially without backward steps, adaptive or iterative models allow modifications during incremental development, and Agile models are flexible customer-focused frameworks using iterative and incremental development.

Further detail

• Design defines the architecture, frameworks, database, functional specifications, layouts, and configurations, while coding writes source code, applies DevOps practices, and includes unit testing.

💡 Memory Hook

Plan → Analyze → Design → Code → Test → Deploy → Maintain

📖 3. Waterfall Model

🔑 Key Concepts & Definitions

• Waterfall Model : A linear sequential predictive model in which each phase must finish before the next begins, with no overlap or return to an earlier phase.

★ Must-know

• The Waterfall Model proceeds through:
  • Requirement analysis
  • System design
  • Implementation
  • Integration and testing
  • Deployment
  • Maintenance

📌 In the Waterfall Model, the output of one phase serves as the input for the next, requirements must be identified correctly upfront, and testing occurs only after development is complete.

Further detail

📌 The Waterfall Model is simple, predictable, and suitable for smaller projects with well-understood requirements, but it is unsuitable for complex or evolving projects because changes and feedback are difficult to accommodate.

💡 Memory Hook

Imagine phases cascading like water over a cliff, with no path upward.

📖 4. V-Model Verification and Validation

🔑 Key Concepts & Definitions

• V-Model : Also called the Verification and Validation Model, a predictive structure in which development and testing proceed in parallel and meet at implementation.

★ Must-know

• The verification side contains:

  • Business requirement analysis
  • System design
  • Architectural design (HLD)
  • Module design (LLD)
  • Coding

• The validation side contains:

  • Unit testing
  • Integration testing
  • System testing
  • User acceptance testing (UAT)

Further detail

• The V-Model identifies defects early, maps development phases to testing phases, avoids Big Bang testing, promotes development-testing collaboration, and requires strict quality checks before deployment.

💡 Memory Hook

Verification builds on the left; validation tests on the right.

📖 5. Incremental Model

🔑 Key Concepts & Definitions

• Incremental Model : Divides software development into several increments, with each increment following requirements, design, coding, testing, and delivery phases.

★ Must-know

• 🔄 The Incremental Model evolves by:
  1. Starting with an initial implementation
  2. Developing important functionalities early
  3. Adding functions to the previous release
  4. Obtaining the final software

Further detail

📌 The Incremental Model uses user feedback to evolve the software, but its requirements must be sufficiently clear for a successful multi-iteration project.

💡 Memory Hook

Initial implementation → feedback → added functions → final software

📖 6. Iterative Model

🔑 Key Concepts & Definitions

• Iterative Model : Develops software through repeated cycles called iterations, with a small part of the software developed at a time.

★ Must-know

• The Iterative Model starts with some requirements, develops software, reviews it, updates it, and repeats the cycle until the final product is achieved.

Further detail

• The Iterative Model was designed to overcome drawbacks of the classical Waterfall Model and is more rigid than Agile because it focuses on incremental improvements.

📌 The Iterative Model provides better control of scope, time, and resources and enables early detection of technical or architectural issues, but limited flexibility and propagated errors can cause rework or technical debt.

💡 Memory Hook

Requirements → development → review → update → repeat

📖 7. Rapid Application Development

🔑 Key Concepts & Definitions

• Rapid Application Development : IBM, 1980s — An adaptive model emphasizing quick iterative release cycles, working software delivered in short timelines, and responsiveness to user feedback and changing requirements.

★ Must-know

• RAD commonly delivers working software in 60–90-day time-boxes and was first proposed by IBM in the 1980s.

• RAD has four phases:
  • Requirements planning
  • User description through prototyping
  • Construction
  • Cutover

📌 RAD offers rapid feedback, lower cycle time and costs, adaptable requirements, and productivity gains, but requires skilled professionals, continuous customer involvement, reusable components, and modular projects.

Further detail

• RAD uses brainstorming and user scenarios for requirements, prototypes for feedback and data validation, automated tools to transform models into working products, and module-interface testing with user acceptance testing during cutover.

💡 Memory Hook

Requirements planning → prototyping → construction → cutover

📊 Synthesis Tables

SDLC Model Comparison

Model	Development approach	Testing or feedback	Main limitation
Waterfall	Sequential phases	Testing after development	Difficult to accommodate change
V-Model	Sequential development with parallel validation	Testing mapped to development stages	Rigid and documentation-heavy
Incremental	Functional increments add to previous releases	User feedback between releases	Requirements must be clear
Iterative	Repeated cycles refine the product	Review and update each cycle	Errors may propagate
RAD	Rapid prototyping and short releases	Continuous stakeholder feedback	Requires skilled professionals and customer involvement