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OCR H446 1.2.3 Waterfall lifecycle and spiral model

Part 1 of 6 · H446 1.2.3 · Software development

H446 1.2.3 asks not what waterfall and spiral are called but what their movement changes for a project. This worksheet traces a linear route and a risk-driven cycle against contrasting briefs, so iteration, risk and change are argued as consequences rather than as labels.

Students will:

  • follow the stages of a waterfall lifecycle and the repeating structure of a spiral cycle
  • explain a benefit and a drawback of waterfall for a project with fixed, signed-off rules
  • design a first spiral cycle with an objective, a major risk and a risk-reduction activity
  • explain how evidence from one cycle changes the plan for the next
  • compare both routes for a project carrying safety and integration risk, then recommend one

Inside: 6 explanation cells, 1 multiple-choice question, 2 fill-in-the-blanks cells and 4 written answers. 36 marks, about 45 to 55 minutes.

Series: H446 1.2.3 · Software development, part 1 of 6.

Shared by Coding PathwayVerified teacher

  • 13 cells
  • About 45 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 15 Sept 2026

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Waterfall lifecycle and spiral model

Software development usually includes requirements, design, implementation, testing, deployment and evaluation. A development methodology describes how a team moves through this work.

In this worksheet, you will compare two models. Waterfall moves through planned stages. Spiral repeats a cycle in which risk influences what the team investigates and develops next.

Read two process routes

Waterfall and risk-driven spiral process routesfollow the movement, then explain its consequenceWATERFALL: planned stage outputsrequirementsagreed needsdesignplanned solutionimplementationworking codetestingtest evidencedeploymentreleased systemClear deliverables and planned stages can make control easier.A misunderstood early requirement can affect several later stages.SPIRAL: repeat responsibilities around the current risks1 set objectivesconstraints and options2 analyse risksreduce uncertainty first3 develop + testchosen increment/prototype4 plan next cycleevidence changes the planIteration is visible, but risk analysis, not repetition alone, drives the spiral.

In the waterfall lifecycle, the team completes planned stages in order. Typical work includes requirements and analysis, design, implementation, testing, deployment and evaluation. Each stage produces a deliverable, such as an agreed requirements document, design or set of test results. This structure can make responsibilities and progress clear. However, a requirement found to be wrong late in development may force changes to several completed stages.

In the spiral model, the team repeats a risk-led cycle. It sets objectives, identifies and investigates important risks, develops and tests an appropriate part or prototype, and then plans the next cycle using the evidence. This can reduce uncertainty before the project makes a large commitment. Specialist risk analysis and repeated planning can also add time and cost.

Worked comparison: archive migration

A council is replacing a system that stores public records. The file format and legal rules are already known.

Why waterfall could help: the team can agree the requirements, design and tests before implementation. Named stages and documents make progress easier to check.

Possible problem: if a missing legal rule is discovered during final testing, the team may need to change the design, code and tests.

Why spiral might help: the team could first test the part of the conversion that carries the greatest risk.

Possible problem: repeated risk analysis and planning may add unnecessary cost when the rules and technology are already well understood.

Multiple choice1 mark

Which action most clearly distinguishes a spiral cycle from merely repeating development work?

  • AIdentifying and resolving the most important project risks before committing to the next approach
  • BWriting all documentation after release
  • CCompleting every project in one fixed pass
  • DAvoiding client evaluation
Fill in the blanks3 marks
Waterfall moves through planned gap 1 with identifiable outputs. Spiral repeats around project gap 2 and plans the next gap 3 from new evidence.
  • stages
  • risks
  • iteration
  • syntax
Written answer6 marks

A payroll system uses fixed tax rules. The requirements and acceptance tests have been formally agreed. Explain one benefit and one drawback of using the waterfall lifecycle for this project.

For each point, name something waterfall does, connect it to the payroll project and explain the result.

Students type their answer here.

Worked spiral cycle: an uncertain sensor

A flood-warning service will use a new sensor. Its readings may be inaccurate in cold weather. A first spiral cycle could be:

  1. Set an objective: show that the service can make reliable warning decisions.
  2. Identify the main risk: inaccurate readings could cause a false alarm or prevent a real warning.
  3. Reduce the risk: build a small prototype and test the sensor at several temperatures.
  4. Plan the next cycle: use the test results to choose calibration work, a different sensor or the next part of the system.

The prototype is built to investigate a named risk. Simply producing several versions does not, by itself, make a project spiral.

Written answer8 marks

A medical appointment system must connect to an unfamiliar identity-checking service. Plan its first spiral cycle. Include: an objective and a way to judge success; a major risk and its possible effect; an activity that investigates or reduces the risk; and how the evidence would affect the next cycle.

Make the four parts form one connected plan. The activity should address the risk you named.

Students type their answer here.

Apply the ideas in a new context

The next questions give less support. Use the project details in each answer and explain why a feature of the methodology helps or causes a problem.

Written answer5 marks

A student writes: ‘Waterfall and spiral are both iterative because developers can correct mistakes. Spiral is always best for a complex project.’ Explain what is wrong with both claims.

First compare how the two models organise development. Then explain why project risk and cost matter when choosing between them.

Students type their answer here.

Written answer9 marks

A rail-signalling simulator involves safety risks and expensive hardware. Some requirements will only become clear during trials. Compare the waterfall lifecycle with the spiral model for this project and recommend one of them.

Explain how each model would organise the work. Apply benefits and drawbacks to safety, hardware trials, changing knowledge and project control. Finish with a supported judgement.

Students type their answer here.

Fill in the blanks4 marks
Waterfall moves through planned checkpoint gap 1 with identifiable deliverables. A requirement discovered late may cause checkpoint gap 2 to earlier documents, code and tests. Spiral uses checkpoint gap 3 analysis to decide what to investigate and develop in the next checkpoint gap 4.

Review your understanding

Check that you can describe what happens in each model, explain when it could help, explain when it could cause difficulty and apply those points to a project rather than repeating a general slogan.