A design has a goal and limits. This shade must cover at least three garden cells. Each cell of shade costs two tokens, and the available tokens are the budget. A good choice must cover enough cells and stay within the budget. The goal is called a criterion. A constraint is a limit that the design must obey, such as a maximum size or budget. Criteria and constraints play different roles in evaluating a design. A criterion describes a desired outcome; a constraint restricts the acceptable design space. Our invented shade model compares covered area with material tokens. Changing the design can improve one measure while creating another problem, so both requirements must be checked together.
Engineering and scientific investigation · Discover & try
What should a design achieve, and what limits it?
Reading level 3 of 5 · IndependentChange
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Criterion
A feature used to judge success.
Constraint
A required limit on possible designs.
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Invented grid coverage and token costs make the performance criterion and budget constraint visible.
What to look for
- It costs only four tokens but does not cover the required three cells.
- It covers three cells and costs exactly six tokens.
- It covers enough cells, but eight tokens is more than the six available.
Explain what you noticed
A delivery robot must carry a parcel and fit through a 30 cm opening. Which statement is a size constraint?
Keep this idea: A solution needs to address the goal and respect its required limits.
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