ARC A · DemandCheck passes
How many slices do all guests need?
36 slices
- Reason
18 × 2 = 36- Check
- The attendee allocation also totals 36.
- Output
- slice demand → parent data
← ARC composition
Self-contained · No dependencies
Worked composition
A checked lunch order
Three small ARCs answer bounded questions. Their checked outputs become data for a larger ARC that decides what to order—and checks the whole composition against the original need.
Inputs
Three focused child ARCs
ARC B · PackageCheck passes
How many slices does one pizza provide?
8 slices
- Reason
- The selected menu item is cut into equal slices.
- Check
- Capacity is a positive whole number.
- Output
- pizza capacity → parent data
ARC C · DietaryCheck passes
How many slices must be gluten-free?
4 GF slices
- Reason
2 × 2 = 4- Check
- GF guests are a subset of all guests.
- Output
- GF demand → parent data
Larger composed ARC
Parent ARC · Order4/4 checks pass
What is the smallest lunch order that covers everyone?
Order 5 pizzas: 1 gluten-free + 4 regular.
- Reason
- The three checked child answers determine demand, package capacity, and dietary allocation.
- Checks
- The parent runs four separate checks against both the child contracts and the original inputs.
3/3 child contracts valid
40 slices ≥ 36 needed
8 GF slices ≥ 4 needed
4 pizzas would be too few
Why this is composition: each child owns one question and check; the parent consumes only their explicit outputs, then verifies the combined result end to end.