# Module 1: Your First Legal Rule In this module, you'll write your first legal rule in L4—a simple legal obligation with conditions, deadlines, and consequences. ## Learning Objectives By the end of this module, you will be able to: - Write a basic legal obligation using PARTY and MUST - Add conditions using IF - Set deadlines using WITHIN - Define consequences using HENCE and LEST - Test your rule using #EVAL --- ## A Simple Legal Obligation Let's start with something every lawyer understands: a simple legal obligation. Find the complete working example later in this document. **The annual return obligation:** "A registered charity must file an annual return." In L4, we write this as: ```l4 GIVEN charity IS A RegisteredCharity `The annual return obligation` MEANS PARTY charity MUST `file annual return` ``` Let's break this down: | Code | Meaning | | ------------------------------------------ | ------------------------------------------ | | `GIVEN charity IS A RegisteredCharity` | This rule applies to registered charities | | `` `The annual return obligation` MEANS `` | The name of this rule | | `PARTY charity` | The charity is the one with the obligation | | `MUST` | This creates a legal obligation | | `` `file annual return` `` | This is what they must do | ### Backtick Names Notice the backticks around `file annual return`. In L4, backticks let you use spaces and special characters in names. These are called **quoted identifiers**. ```l4 -- These are equivalent ways to name things: fileReturn -- camelCase (no spaces) `file return` -- quoted identifier (with spaces) `file annual return` -- more descriptive ``` Use backticks when you want names that read like natural language. --- ## Try It Yourself Write a rule that says "A solicitor must maintain client confidentiality." Hint: You'll need to: 1. Define a `DECLARE` for the Solicitor type 2. Define `DECLARE` for the Actor and Action types 3. Use `PARTY ... MUST ...` to create the obligation --- ## Adding Conditions Real legal rules have conditions. Let's add one: ```l4 IF charity's status EQUALS Active PARTY charity MUST `file annual return` ``` The `IF` keyword adds a condition that must be true for the obligation to apply. ### Multiple Conditions Use `AND` and `OR` for multiple conditions: ```l4 IF charity's status EQUALS Active AND charity's income > 10000 ``` ### Accessing Fields The `'s` syntax accesses fields of a record: ```l4 charity's status -- the status field of charity charity's income -- the income field of charity ``` --- ## Setting Deadlines Legal obligations usually have deadlines. Use `WITHIN`: ```l4 PARTY charity MUST `file annual return` WITHIN 60 ``` `WITHIN 60` means "within 60 days." L4 uses days as the default time unit. --- ## Consequences: HENCE and LEST What happens when someone complies or doesn't comply? Use `HENCE` and `LEST`: ```l4 PARTY charity MUST `file annual return` WITHIN 60 HENCE FULFILLED LEST BREACH ``` | Keyword | Meaning | | ------- | ------------------------------------- | | `HENCE` | What happens if they **comply** | | `LEST` | What happens if they **don't comply** | ### Chaining Obligations `HENCE` can trigger another obligation: ```l4 PARTY seller MUST `deliver goods` WITHIN 14 HENCE PARTY buyer MUST `pay invoice` WITHIN 30 HENCE FULFILLED LEST BREACH LEST BREACH ``` This creates a chain: if the seller delivers, the buyer must pay. --- ## Complete Example ```l4-file -- Module 1: Your First Legal Rule - Complete Examples -- All examples are validated and use natural language identifiers -- ============================================================================= -- SECTION 1: Basic Obligation (simplified for teaching) -- ============================================================================= -- Define types needed for obligations DECLARE `Charity Status` IS ONE OF Active Suspended Dissolved DECLARE `Registered Charity` HAS `the name` IS A STRING `the status` IS A `Charity Status` `the annual income` IS A NUMBER -- Define actors and actions DECLARE Party IS ONE OF `the charity` `the buyer` `the seller` `the Commissioner` DECLARE Action IS ONE OF `file the annual return` `deliver the goods` `pay the invoice` HAS amount IS A NUMBER `cancel the order` `issue a Required Steps Notice` -- ============================================================================= -- SECTION 2: The Annual Return Obligation -- ============================================================================= -- A charity's obligation to file an annual return GIVEN charity IS A `Registered Charity` GIVETH A DEONTIC Party Action `the annual return obligation` MEANS IF charity's `the status` EQUALS Active THEN PARTY `the charity` MUST `file the annual return` WITHIN 60 HENCE FULFILLED LEST PARTY `the Commissioner` MAY `issue a Required Steps Notice` HENCE FULFILLED ELSE FULFILLED -- ============================================================================= -- SECTION 3: Chained Obligations - Sale Contract -- ============================================================================= -- The seller must deliver, then the buyer must pay GIVETH A DEONTIC Party Action `the sale contract` MEANS PARTY `the seller` MUST `deliver the goods` WITHIN 14 HENCE PARTY `the buyer` MUST `pay the invoice` 1000 WITHIN 30 HENCE FULFILLED LEST BREACH LEST PARTY `the seller` MAY `cancel the order` HENCE FULFILLED -- ============================================================================= -- SECTION 4: Test Data -- ============================================================================= `Animal Welfare Society` MEANS `Registered Charity` "Animal Welfare Society" Active 50000 -- ============================================================================= -- SECTION 5: Tests -- ============================================================================= -- Test field access #EVAL `Animal Welfare Society`'s `the name` #EVAL `Animal Welfare Society`'s `the status` EQUALS Active #EVAL `Animal Welfare Society`'s `the annual income` > 10000 -- Test obligation - charity files on time #TRACE `the annual return obligation` `Animal Welfare Society` AT 0 WITH PARTY `the charity` DOES `file the annual return` AT 30 -- Test sale contract - happy path #TRACE `the sale contract` AT 0 WITH PARTY `the seller` DOES `deliver the goods` AT 10 PARTY `the buyer` DOES `pay the invoice` 1000 AT 25 ``` Included are: - Type definitions for charities, actors, and actions - The annual return obligation with conditions and deadlines - A chained sale contract - Test data and `#TRACE` simulations ### Understanding GIVETH A DEONTIC When a function returns an obligation (not just a value), we use `GIVETH A DEONTIC`: - `GIVETH A BOOLEAN` - returns true/false - `GIVETH A NUMBER` - returns a number - `GIVETH A DEONTIC Actor Action` - returns an obligation (specifying actor and action types) --- ## Testing with #EVAL Use `#EVAL` to test expressions: ```l4 #EVAL testCharity's name -- Result: "Animal Welfare Society" #EVAL testCharity's status EQUALS Active -- Result: TRUE ``` In VS Code with the L4 extension, hover over `#EVAL` to see the result. --- ## Testing with #TRACE For regulative rules (obligations), use `#TRACE` to simulate scenarios: ```l4 #TRACE `annual return obligation` testCharity AT 0 WITH PARTY testCharity DOES `file annual return` AT 30 ``` This simulates: - Starting at day 0 - The charity filing their return at day 30 The result shows whether the obligation was `FULFILLED` or `BREACH`. --- ## Common Mistakes ### 1. Missing Type Declaration ```l4 -- ❌ Wrong: Type not declared GIVEN charity IS A RegisteredCharity -- ✅ Right: Declare the type first DECLARE RegisteredCharity HAS name IS A STRING ``` ### 2. Wrong Field Access ```l4 -- ❌ Wrong: Missing 's IF charity status EQUALS Active -- ✅ Right: Use 's for field access IF charity's status EQUALS Active ``` ### 3. Missing Backticks for Multi-Word Names ```l4 -- ❌ Wrong: Spaces without backticks MUST file annual return -- ✅ Right: Use backticks MUST `file annual return` ``` ## Exercises ### Exercise 1: Simple Obligation Write an L4 rule for: "An employee must submit a timesheet every week." ### Exercise 2: Conditional Obligation Write an L4 rule for: "If a tenant is more than 14 days late on rent, the landlord may issue an eviction notice." ### Exercise 3: Chained Obligations Write L4 rules for: "The seller must deliver goods within 14 days. If delivered, the buyer must pay within 30 days." --- ## Summary In this module, you learned: | Concept | Syntax | | --------------------- | --------------------------------- | | Declare parameters | `GIVEN name IS A Type` | | Create obligation | `PARTY actor MUST action` | | Add condition | `IF condition` | | Set deadline | `WITHIN days` | | Compliance result | `HENCE consequence` | | Non-compliance result | `LEST consequence` | | Test expression | `#EVAL expression` | | Simulate scenario | `#TRACE rule AT time WITH events` | --- ## What's Next? In [Module 2: Legal Entities](/l4/courses/foundation/module-2-entities.md), you'll learn how to model complex legal entities with proper types, including records, enums, and relationships between entities.