Waterfall methodology

As explained in Lead Developer Career Guide

A linear, sequential project-management and software-development methodology in which predefined stages are completed in order before the next stage begins.

Waterfall is a linear, sequential approach to software development. Teams complete predefined stages in order, typically using detailed plans and fixed requirements. It suits projects with clear scope and a well-defined end goal. section 7.1.1 section 7.1.3

A typical waterfall project moves through these stages:

• Gather requirements. section 7.1.1
• Design the solution. section 7.1.1
• Implement the design. section 7.1.1
• Test the software, then maintain it by addressing bugs or other problems. section 7.1.1

Figure 7.1 Waterfall method phases

View the phases as a sequence, with each stage completed before the next begins. section 7.1.1

Upfront planning and stakeholder sign-offs can help control scope and clarify expectations. The trade-off is that changes become harder after a phase is complete and may add delays or costs. Unlike waterfall, agile expects change and delivers work incrementally; the right choice depends on project needs and organizational culture. section 7.1.1 section 7.1.3

Table 7.2 Agile vs. waterfall (view table figure)

Criteria	Agile	Waterfall
Definition	An iterative and flexible approach to project management that emphasizes collaboration, adaptability, and customer satisfaction	A linear and sequential approach to project management that emphasizes planning, documentation, and strict control
Focus	Customer satisfaction and delivering value	Meeting project requirements and staying within budget
Planning	Continuous planning throughout the project	Comprehensive planning at the beginning of the project
Requirements	Requirements not fixed and can change as the project progresses	Requirements fixed and defined at the beginning of the project
Testing	Continuous testing throughout the project	Testing at the end of each phase
Feedback	Regular feedback from customers and stakeholders	Limited feedback from customers and stakeholders
Risk management	Constantly monitoring and mitigating risks	Risk management done at the beginning of the project
Time frame	Shorter development cycles (two to four weeks)	Longer development cycles (three to six months or longer)

Compare waterfall and agile across planning, requirements, testing, and feedback. section 7.1.3

Calculating a waterfall defect rate

For a waterfall project with 1,000 lines of code and 150 defects, divide defects by lines of code and multiply by 100: the defect rate is 15%. section 7.4.3

How Lead Developer Career Guide covers it

How deep it goes

Defines five sequential phases and discusses planning benefits, change costs, and defect-rate calculation, but not detailed phase procedures.

Examples

Uses Windows development as a staged project example and calculates a 15% defect rate from 150 defects across 1,000 lines of code.

What you can do after

Evaluate whether sequential delivery fits fixed requirements and clear scope, and calculate a defect rate from defects and lines of code.

How it connects

Compares waterfall with agile and connects its testing phase to defect rates, code reviews, and software testing.

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Also explained in

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  Delivering Machine Learning Projects: From design to deploymentWaterfall is a sequential software development methodology in which requirements, design, implementation, testing, and acceptance proceed in ordered stages.
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  Think Like a CTOA project-development approach that plans and defines as much as possible before implementation begins and proceeds through largely sequential stages.

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Related concepts

• agile software developmentcontrasts with · Agile software development is an iterative approach that delivers software incrementally through collaboration, feedback, adaptive planning, and responsiveness to change.
• requirements analysishas part · Requirements analysis is the systematic process of eliciting, clarifying, assessing, and documenting the needs and constraints a system or product must satisfy.
• testhas part · A test is a procedure or check that evaluates behavior using specified inputs or evidence against expected results or criteria.
• error rateuses · Error rate is the proportion of evaluated operations, cases, or outcomes that produce an error or fail a specified criterion.

This explainer was generated by Manning's knowledge graph from the text of Lead Developer Career Guide. The section links point to the parts of the book it draws on.