Rocket spreads the six practice cards across the floor. "Rules one at a time are slow," he says. "Let us chain them."
Raven draws a box at the top of a big sheet of paper and writes: "Streak?"
"Yes goes left, no goes right," she says. "Each answer leads to the next question."
Nova hovers above the sheet. "That is a decision tree," she says. "Which question should come first?"
Rocket taps the streak box. "The one that sorts out a whole group at once!"
They start drawing branches.
You will build Sky Sorter's first decision tree on paper.
Then you will run all six practice cards through it and record the labels.
The tree uses three tests, one for each feature.
| Card | Brightness | Size | Streak? | Tree label |
|---|---|---|---|---|
| A | 120 | 2 | no | |
| B | 230 | 5 | no | |
| C | 90 | 12 | no | |
| D | 180 | 1 | yes | |
| E | 210 | 3 | no | |
| F | 150 | 9 | no |
Raven says card E is really a bright star, not a planet.
The tree still followed its rules exactly. The problem is in the rules, not in the following.
| Lab result | True or false? |
|---|---|
| The tree labeled card C a comet. | ? |
| Card D never reached the size question. | ? |
| The tree labeled two cards as stars. | ? |
| Every card ended at exactly one label. | ? |
Brilliant building! Tomorrow we turn the tree into pseudocode.