Paper 2 • Computational Thinking • Devise an abstract model

Do Now!

  • Abstraction helps us simplify reality so a model becomes more useful for a specific purpose.
  • In exams, you may need to devise an abstract model for different scenarios.

Today's Big Idea

Good abstractions remove unnecessary detail, highlight what matters, and match the needs of the audience.

Remove detail Leave out information that does not help the user solve the problem.
Highlight purpose Use labels, colours, symbols or layout to make key features clearer.
Represent simply Flowcharts, diagrams and variable names all stand in for something more complex.

Activity 1: Match the Key Terms

Drag each term into the definition that matches it best.

Abstraction
Abstract model
Flowchart
Variable
Purpose
Tourist map
Term Definition
The process of simplifying something by removing unnecessary detail.
A simplified representation of a real situation, system or process.
A diagram that uses shapes and arrows to represent the logic of a program.
A label for a memory location rather than the binary data stored underneath.
The reason a model exists and the audience it is designed to help.
An example of an abstraction that highlights routes and landmarks instead of every real-world detail.

Activity 2: Sort the Abstraction Decisions

Place each statement into the abstraction method it demonstrates most clearly.

A tourist map leaves out the exact shapes of streets and buildings.
Bright colours are used so different lines are easy to follow.
A flowchart uses a diamond instead of writing out full code for a decision.
The variable names a, b and c stand in for binary values in memory.
A programmer hides the binary detail when writing a = b - c.
Station names and interchange points are made clearer than parks or house numbers.
Labels and icons are added so a model is more useful for its audience.
A simplified diagram becomes a model of the original system.

Remove detail

Highlight what matters

Represent simply

Activity 3: Create the Abstract Model

Use the example flowchart on this page to explain how you would create a suitable abstract model for a new situation.

Scenario:

  • A student wants to model how a school login system decides whether to let a user into the network.
  • Explain what key steps and decisions would need to appear in a flowchart, such as checking the username, password, or whether the account is locked.
  • Describe how the flowchart acts as an abstract model by simplifying the real system into clear inputs, decisions and outcomes.
  • Explain why a flowchart is a suitable model for this problem and what detail would be left out.
Flowchart for a lamp fault A simplified decision-making flowchart that abstracts the logic of checking why a lamp does not work. Lamp doesn't work Is the lamp plugged in? NO Plug in the lamp YES Is the bulb broken? YES Replace bulb NO Repair lamp
Start by naming the real system you are modelling. Then explain the main inputs, the decision boxes you would include, and the possible outputs. You could use sentence starters like: "The flowchart would begin with...", "A decision box would check whether...", "If the answer is yes/no, then...", and "This is an abstract model because...".