Northbridge: from first permit to a complete case

25 chapters · 6 stages · Worked solutions

Learn Law DSL through the work of a fictional municipality. Start with a resident applying for a permit; follow the case through missing facts, conflicting documents, time limits, obligations, and appeal. Each chapter includes code, observed results, an exercise, and a worked solution.

Start with the first permit · Browse worked solutions

Your route through Northbridge

Read the core route in order. Take the mathematics branch when you need quantities and exact computation; return to the advanced chapters for composition and modeling practice. The illustrations set the scene; the code and observed results establish how the model behaves.

BeginnerIntermediateAdvancedMathematics branchAdvanced IIModeling practice

Beginner

Build a first rule, distinguish unknown from false, handle exceptions, and compute a fee.

1. First permit: facts, a rule and a question
2. Why a missing fact is not a refusal
3. Exceptions and conflicting rules
4. The permit fee

Intermediate

Model applicants, registers, documents, editions, deadlines, and legal effects.

5. Who counts as a suitable applicant
6. When the register may stay silent
7. A document is not yet a proven fact
8. Which edition applies and when the term expires
9. From permit to duties and powers

Advanced

Coordinate a procedure, compare readings, allocate in rounds, and explain a result.

10. A procedure with parallel checks
11. Appeal: reading, judgment and precedent
12. Allocation in rounds
13. Repeatable norms without copying
14. Why this answer and what would change it

Mathematics branch

Work with dimensions, exact bounds, and numeric support limits.

15. Quantities and dimensions
16. Exact computation and proven bounds
17. Numeric families and support boundaries

Advanced II

Compose packages and work with presumptions, sources, evidence, queries, and standard functions.

18. Vocabulary and package composition
19. Unknown, presumed and deemed: negation, closure, presumptions, fictions, constraints
20. Sources, time, and outside data
21. Positions live, files move, readings decide
22. Expansions you can answer about, answers you can explain
23. Numbers and the standard library: every figure the 0.2 machine proves

Modeling practice

Choose between neighboring constructs, then follow one case through five changes.

24. Neighbor constructs, nine mistakes and three decision tasks
25. Capstone case: one file, five steps, three worlds

Before you start

You should be comfortable reading code and running terminal commands. Begin with the first-package tutorial if this is your first encounter with executable rules.

Northbridge is a synthetic, unofficial teaching world. The recorded runs use law 0.1.0, law.core/0.2, and standard library 0.2.0. Later numeric profiles are discussed with their observed support limits; an expected refusal is not a successful calculation.

Learn by predicting

Before a command, predict the answer. After the run, explain which fact or rule made the difference. Change one condition and predict again. Open the worked solution after attempting the exercise; each chapter links to its corresponding solution.