Thinking abstractly: choosing the detail that matters

A map is a simplified model of a real place. It keeps the details that help someone use the map and leaves out details that are not needed for that purpose. This process is called abstraction.

By the end, you will be able to

• define abstraction using relevant and irrelevant detail;
• explain why the purpose of a model changes what it should include;
• distinguish abstraction from decomposition and from careless simplification;
• design and justify an abstract model for a new situation.

Remember: a model represents selected features of something else. It is not the real thing.

Abstraction acts as a purpose filter

The cycling map retains routes, gradients, safe crossings and closures because they affect route choice. It omits shop-window colours and building interiors because they do not help a cyclist choose a route.

The omitted details still exist in reality. They are simply unnecessary for this model. If the purpose changed to planning shop deliveries, loading entrances would become relevant. A detail is therefore relevant only when it helps the model serve its user and purpose.

An abstract model might be shown as a map, graph, flowchart, table or program interface. Abstraction decides which information to include. Visualisation decides how information is presented. A diagram can use both, but the words do not mean the same thing.

Worked method

Purpose: help a cyclist choose an accessible route.

1. Identify the user and decision. The cyclist must compare possible routes.
2. Keep relevant details. Surface, gradient, crossings, closures and distance affect that decision.
3. Leave out irrelevant details. Building decoration and unrelated shop information do not affect it.
4. Recognise a limitation. A temporary obstacle could make the map inaccurate until its data is updated.

A full explanation links the design choice to its result. Removing irrelevant details means that less information has to be stored, processed and displayed. This can reduce development work and make routes easier for the cyclist to compare. The statement “it saves time” is too vague because it does not say whose time is saved or why.

Guided practice: improve a poor model

A draft route model stores the paint colour of every nearby building, every advert and the number of windows on each building, but it does not store gradients.

First remind yourself of the purpose: helping a cyclist choose an accessible route. Then choose one detail to remove and one useful detail to add. Explain how each change helps the cyclist make the decision.

Independent transfer: an event map

A music event needs an interactive venue map that attendees can open on a phone using an app or web browser. The map must also support people who need step-free routes. Devise the model rather than listing everything that exists at the venue.

Checkpoint

Complete the explanation from memory. Use the precise terms you have learned; your teacher will review your answers.

Review your understanding

Before submitting, check that you can define abstraction, identify relevant and irrelevant detail for a stated purpose, and explain one benefit or limitation in the context of a model.