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Linear Sequential Model in SDLC: The Waterfall Model

Linear Sequential Model in SDLC: The Waterfall Model

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Oct 1, 2026

The linear sequential model is also known as the Waterfall model. In Waterfall, activities like requirements, design, implementation, testing, and maintenance are performed in a rigid order with little/no overlap, matching the “linear sequential” description. The Waterfall model is explicitly described as “linear-sequential” in SDLC references. Correct option: (iii) Waterfall Model.3

Key terms

  • Waterfall model
  • SDLC
  • Requirements
  • Phase dependency

Footnotes

  1. SDLC - Waterfall Model - States Waterfall is referred to as a linear-sequential life cycle model and phases don’t overlap. ↩

  2. What is a Waterfall model? Definition and guide | TechTarget - Defines Waterfall as a linear, sequential approach with dependent steps and rigid progression. ↩

  3. SDLC - Waterfall Model - Explains that any phase begins only if the previous phase is complete and the process is linear sequential. ↩

Why “Linear Sequential Model” Maps to Waterfall

  1. 1
    Step 1

    Linear sequential means phases follow a strict order: each phase begins after the previous phase is completed.

  2. 2
    Step 2

    Waterfall requires completing each phase before starting the next, which directly matches the linear sequential definition.2

    Footnotes

    1. What is a Waterfall model? Definition and guide | TechTarget - Defines Waterfall as a linear, sequential approach with dependent steps and rigid progression. ↩

    2. SDLC - Waterfall Model - Explains that any phase begins only if the previous phase is complete and the process is linear sequential. ↩

  3. 3
    Step 3

    Typical Waterfall flow uses requirements → design → implementation → verification/testing → maintenance, presented as a cascading sequence.2

    Footnotes

    1. What is the Waterfall Methodology? | Atlassian - Describes Waterfall as linear, sequential with five cascaded stages (requirements, design, implementation, verification, maintenance). ↩

    2. SDLC - Waterfall Model - Explains that any phase begins only if the previous phase is complete and the process is linear sequential. ↩

  4. 4
    Step 4

    Agile and Spiral are iterative/risk-driven rather than strictly linear, and RAD emphasizes rapid prototyping and timeboxed iterations.3

    Footnotes

    1. What Is Agile? | Atlassian - Background on Agile focusing on iterative delivery and feedback (contrasts with rigid linear progression). ↩

    2. What Is Rapid Application Development (RAD Model) - Describes RAD as prioritizing rapid prototyping and feedback with agile-leaning iterations. ↩

    3. Rapid Application Development and the future of IT - Simplifier AG - Provides RAD/timeboxing context and contrasts iteration-based approaches with traditional linear methods (and references the broader iterative modeling landscape). ↩

How Waterfall Executes in a Linear Sequence

Requirements

Phase 1

Define and document requirements up front."

Design

Phase 2

Produce design artifacts based on requirements."

Implementation

Phase 3

Build the system from the design."

Verification/Testing

Phase 4

Test after implementation to verify correctness."

Maintenance

Phase 5

Operate and maintain the delivered system."

Model Fit to “Linear Sequential” Meaning

Qualitative fit: how closely the model follows strict phase-by-phase linear progression.

Quick comparison of options

OptionTypical behaviorDoes it match “linear sequential”?
(i) Agile ModelIterative development with feedback loops, not a strict one-way phase cascadeNo (not primarily linear sequential)
(ii) Spiral ModelIterative cycles centered on risk assessment and prototypingNo (risk-driven iterations, not single pass)
(iii) Waterfall ModelLinear, sequential approach; each phase completes before the next beginsYes2
(iv) RAD ModelIterative development with rapid prototyping and user feedbackNo (rapid prototypes/timeboxed iterations)

Footnotes

  1. What Is Agile? | Atlassian - Background on Agile focusing on iterative delivery and feedback (contrasts with rigid linear progression). ↩

  2. Rapid Application Development and the future of IT - Simplifier AG - Provides RAD/timeboxing context and contrasts iteration-based approaches with traditional linear methods (and references the broader iterative modeling landscape). ↩

  3. What is a Waterfall model? Definition and guide | TechTarget - Defines Waterfall as a linear, sequential approach with dependent steps and rigid progression. ↩

  4. SDLC - Waterfall Model - Explains that any phase begins only if the previous phase is complete and the process is linear sequential. ↩

  5. What Is Rapid Application Development (RAD Model) - Describes RAD as prioritizing rapid prototyping and feedback with agile-leaning iterations. ↩

Common exam-style clarifications

Exam Shortcut

If the question says “linear sequential model”, immediately think Waterfall—because Waterfall is commonly defined as linear and sequential with phase dependency (no overlapping).2

Footnotes

  1. What is a Waterfall model? Definition and guide | TechTarget - Defines Waterfall as a linear, sequential approach with dependent steps and rigid progression. ↩

  2. SDLC - Waterfall Model - Explains that any phase begins only if the previous phase is complete and the process is linear sequential. ↩

Knowledge Check

Question 1 of 3
Q1Single choice

Which model is also known as the linear sequential model?

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