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Foundation Course

A complete introduction to L4 for beginners. No programming experience required.

Overview

This course takes you from zero to writing your first legal rules in L4. You'll learn:

  • How to write legal rules that computers can understand and execute
  • How to model legal entities and relationships
  • How to handle multi-step legal processes
  • How to test and simulate legal scenarios

Prerequisites: Basic familiarity with legal concepts. No programming experience required.

Time: Approximately 4-6 hours total

Modules

Module 0: Introduction

What is L4 and why use it?

  • What L4 is designed for
  • How L4 differs from traditional legal drafting
  • Setting up your environment

Time: 15 minutes

Write a simple legal obligation in L4.

  • The basic structure: GIVEN, PARTY, MUST
  • Adding conditions with IF
  • Setting deadlines with WITHIN
  • Consequences: HENCE and LEST

Time: 45 minutes

Model structured legal entities and relationships.

  • From strings to structured types with DECLARE
  • Enumerating legal categories with IS ONE OF
  • Connecting multiple entities
  • Record field access

Time: 60 minutes

Module 3: Control Flow

Handle conditional logic and pattern matching.

  • IF/THEN/ELSE expressions
  • Pattern matching with CONSIDER
  • Working with lists
  • Boolean logic and operators

Time: 45 minutes

Module 4: Functions

Define reusable legal rules and computations.

  • Function signatures with GIVETH
  • Simple functions with MEANS
  • Decision functions with DECIDE
  • Local definitions with WHERE

Time: 60 minutes

Module 5: Regulative Rules

Model obligations, permissions, and prohibitions.

  • The DEONTIC type
  • MUST, MAY, and SHANT
  • Chaining obligations with HENCE/LEST
  • Testing with #TRACE

Time: 60 minutes

Module 6: Putting It Together

Build a complete legal model.

  • Combining everything learned
  • Best practices
  • Common patterns
  • Next steps

Time: 45 minutes

Learning Path

Module 0 ──► Module 1 ──► Module 2 ──► Module 3
                                           │
                                           ▼
              Module 6 ◄── Module 5 ◄── Module 4

Each module builds on the previous ones. Complete them in order for the best learning experience.

After This Course

Once you complete the Foundation Course, you can:

  1. Advanced Course - Deep dives into complex L4 patterns
  2. Tutorials - Task-focused guides for specific goals
  3. Reference - Look up specific language features

Additional examples in the repository:

  • jl4/examples/legal/ - Real-world legal examples
  • jl4/examples/ok/ - Working code samples

Getting Help