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OCR H446 2.1.1 Devising and evaluating abstract models

Part 2 of 2 · H446 2.1.1 · Thinking abstractly

Beyond selecting detail, OCR H446 2.1.1 asks students to devise abstract models and then judge them. Racing-game opponents, two journey-time models and a venue queue make the model boundary and its assumptions the thing under evaluation.

Students will:

  • state the entities, properties and rules a model needs to meet its purpose
  • draw a model boundary and say what is deliberately left outside it
  • tell a limitation of a model apart from a fault in its code
  • compare two models on data required, processing complexity and likely accuracy, then recommend one
  • devise a queue model and state the limitation its assumptions create

Inside: 7 explanation cells, 1 multiple-choice question, 1 fill-in-the-blanks cell and 3 written answers. 23 marks, about 25 to 35 minutes.

Series: H446 2.1.1 · Thinking abstractly, part 2 of 2.

Shared by Coding PathwayVerified teacher

  • 12 cells
  • About 30 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 3 Sept 2026

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The whole resource, exactly as a class sees it. Answers and marking are held back.

Devising and evaluating abstract models

A racing game needs computer-controlled opponents. Its model must be detailed enough to create believable decisions but simple enough to run and develop.

By the end, you will be able to

  • define a model’s entities, properties, rules, boundary and assumptions;
  • compare an abstraction with reality;
  • explain how an omission or assumption limits a result;
  • devise and evaluate a model against its stated purpose.

Reactivate: purpose determines which details are relevant.

Put a boundary around the model

Model boundary and assumptionsRacing opponent model boundaryspeedroute positioncollision ruleOutside modeltyre wearreal weatherengine damageAssumption: one grip value is sufficient for this game mode.

Inside the boundary are details the program represents. Outside are real features deliberately omitted. An assumption states something the model treats as true, such as one grip value being sufficient.

A limitation is a consequence of this selection. It is not automatically a coding error: the model may run exactly as designed but still behave less realistically in rain because real weather is outside its boundary.

Worked model: build from purpose

Purpose: create an opponent that completes a short arcade race believably.

  • Entity: opponent vehicle.
  • Properties: route position, speed, target lane and grip value.
  • Rules: accelerate towards a target speed; slow near a sharp corner; avoid an occupied lane.
  • Boundary: one race and supplied track data.
  • Assumption: the same grip value applies throughout.
  • Limitation: changing surfaces cannot affect grip, so some cornering behaviour may feel unrealistic.

Notice the final link: omitted surface variation → fixed grip → less realistic cornering.

Multiple choice1 mark

Which option is a model limitation rather than necessarily a programming bug?

  • AThe code uses an undefined variable.
  • BThe model assumes every surface has equal grip.
  • CA loop never terminates.
  • DA function is called with the wrong number of parameters.
Written answer4 marks

The same game adds a realistic simulation mode. Explain two details that may need to move inside the model boundary.

For each detail, explain the behaviour it would allow the model to represent.

Students type their answer here.

Guided comparison

Model A predicts journey time using distance ÷ constant speed. Model B also includes time of day, route type and current closures.

Compare them on the same criteria: required data; processing complexity; likely accuracy; and situations in which each remains useful. More detail is not automatically better if the required data is unavailable or the purpose needs only a quick estimate.

Written answer6 marks

Compare Model A and Model B for giving a cyclist a quick journey estimate. Reach a recommendation.

Discuss both models using at least two common criteria before concluding.

Students type their answer here.

Independent model: venue-entry queues

A venue wants a model that predicts approximate waiting time before an event. Available data includes number waiting, average checks per minute, number of open lanes, individual bag contents, staff experience and weather.

Written answer8 marks

Devise an abstract queue model. State its purpose, at least three retained properties, one rule, two assumptions or suppressed details, and one resulting limitation.

Your limitation must follow from an assumption or omission.

Students type their answer here.

Checkpoint

Complete the model critique without looking back. There is no answer bank, and correctness is withheld until teacher review.

Fill in the blanks4 marks
The model checkpoint gap 1 separates represented details from omitted reality. A statement treated as true is an checkpoint gap 2. A resulting weakness is a checkpoint gap 3. Adding more detail is not automatically useful when the purpose or available checkpoint gap 4 does not require it.

Review your understanding

Before submitting, check that you can explain the main distinction in your own words, apply it in an unfamiliar context and justify the resulting behaviour or consequence.