|
| 1 | +--- |
| 2 | +title: "Getting Started with RIDDL" |
| 3 | +description: "A basic introduction to RIDDL concepts and syntax" |
| 4 | +--- |
| 5 | + |
| 6 | +# Getting Started with RIDDL |
| 7 | + |
| 8 | +This tutorial introduces the fundamental concepts of RIDDL through simple |
| 9 | +examples. After completing this tutorial, you'll understand: |
| 10 | + |
| 11 | +- How to structure a RIDDL specification |
| 12 | +- The core building blocks: domains, contexts, entities |
| 13 | +- How to define types and messages |
| 14 | +- Basic handler patterns |
| 15 | + |
| 16 | +## Your First RIDDL Specification |
| 17 | + |
| 18 | +Every RIDDL specification starts with a domain. A domain represents a |
| 19 | +knowledge area or business capability: |
| 20 | + |
| 21 | +```riddl |
| 22 | +domain Greeting is { |
| 23 | + context HelloWorld is { |
| 24 | + // Context contents go here |
| 25 | + } |
| 26 | +} |
| 27 | +``` |
| 28 | + |
| 29 | +## Adding Types |
| 30 | + |
| 31 | +Types define the data structures in your domain: |
| 32 | + |
| 33 | +```riddl |
| 34 | +domain Greeting is { |
| 35 | + context HelloWorld is { |
| 36 | + type Name is String |
| 37 | + type Greeting is { |
| 38 | + recipient: Name, |
| 39 | + message: String |
| 40 | + } |
| 41 | + } |
| 42 | +} |
| 43 | +``` |
| 44 | + |
| 45 | +## Defining an Entity |
| 46 | + |
| 47 | +Entities are stateful objects that respond to commands and emit events: |
| 48 | + |
| 49 | +```riddl |
| 50 | +domain Greeting is { |
| 51 | + context HelloWorld is { |
| 52 | + type Name is String |
| 53 | +
|
| 54 | + entity Greeter is { |
| 55 | + state GreeterState of Greeter.State |
| 56 | +
|
| 57 | + record State is { |
| 58 | + greetingsCount: Integer |
| 59 | + } |
| 60 | +
|
| 61 | + command SayHello is { to: Name } |
| 62 | + event HelloSaid is { to: Name, message: String } |
| 63 | +
|
| 64 | + handler GreeterHandler is { |
| 65 | + on command SayHello { |
| 66 | + send event HelloSaid( |
| 67 | + to = @SayHello.to, |
| 68 | + message = "Hello, " + @SayHello.to + "!" |
| 69 | + ) to Greeter |
| 70 | + } |
| 71 | + } |
| 72 | + } |
| 73 | + } |
| 74 | +} |
| 75 | +``` |
| 76 | + |
| 77 | +## Key Concepts Illustrated |
| 78 | + |
| 79 | +### Domains |
| 80 | + |
| 81 | +Domains group related concepts and provide namespace isolation. A real |
| 82 | +system might have domains like `Sales`, `Inventory`, `CustomerService`. |
| 83 | + |
| 84 | +### Contexts |
| 85 | + |
| 86 | +Bounded contexts define clear boundaries within a domain. Each context has |
| 87 | +its own ubiquitous language - the same term can mean different things in |
| 88 | +different contexts. |
| 89 | + |
| 90 | +### Entities |
| 91 | + |
| 92 | +Entities are the core business objects. They: |
| 93 | +- Have identity (each instance is unique) |
| 94 | +- Have state (data that changes over time) |
| 95 | +- Have behavior (handlers that process commands) |
| 96 | + |
| 97 | +### Types |
| 98 | + |
| 99 | +RIDDL supports rich type definitions: |
| 100 | +- Simple types: `type UserId is UUID` |
| 101 | +- Records: `type Address is { street: String, city: String }` |
| 102 | +- Enumerations: `type Status is any of { Pending, Active, Closed }` |
| 103 | +- Alternations: `type Response is one of { Success, Failure }` |
| 104 | + |
| 105 | +### Messages |
| 106 | + |
| 107 | +Commands and events are the primary communication mechanism: |
| 108 | +- **Commands** - Requests to perform an action |
| 109 | +- **Events** - Facts that have occurred |
| 110 | +- **Queries** - Requests for information |
| 111 | +- **Results** - Responses to queries |
| 112 | + |
| 113 | +## Next Steps |
| 114 | + |
| 115 | +Now that you understand the basics, explore the |
| 116 | +[Reactive BBQ Case Study](rbbq/index.md) to see how these concepts apply |
| 117 | +to a real-world domain model. |
| 118 | + |
| 119 | +For detailed syntax, see the [Language Reference](../references/language-reference.md). |
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