Description

n8n-nodes-dmn

This is an n8n community node that provides DMN (Decision Model and Notation) decision table functionality following the DMN 1.3 specification.

This node is inspired by Dmsrdnv's n8n-nodes-dmn work, but uses a slightly different design approach (one in- and output) and functions without external dependencies.

Features

• DMN 1.3 Compliant: Implements decision tables following the DMN 1.3 specification
• Multiple Hit Policies: Supports UNIQUE, FIRST, PRIORITY, ANY, COLLECT, RULE_ORDER, and OUTPUT_ORDER
• Aggregation Functions: For COLLECT hit policy, supports SUM, COUNT, MIN, MAX aggregations
• FEEL Expressions: Basic support for FEEL-like expressions in conditions
• Type Safety: Automatic type conversion based on column definitions
• Debugging Support: Optional metadata and execution trace for debugging

Screenshot

Installation

Community Node (recommended)

1. Open your n8n instance
2. Go to Settings > Community Nodes
3. Search for @that-one-tom/n8n-nodes-dmn
4. Click Install

Manual Installation

# Navigate to your n8n custom nodes folder
cd ~/.n8n/nodes

# Clone this repository
git clone https://github.com/that-one-tom/n8n-nodes-dmn.git

# Install dependencies
cd n8n-nodes-dmn
npm install

# Build the node
npm run build

# Restart n8n

Usage

Basic Decision Table

The DMN node allows you to create and evaluate decision tables. Here's a simple example:

Input Columns

• age (number)
• country (string)

Output Columns

• discount (number)
• eligible (boolean)

Rules

Configuration

1. Operation: Choose between:

   • Evaluate: Evaluate input items against the decision table
   • Build Table: Output the decision table configuration

2. Hit Policy: Select how to handle multiple matching rules:

   • UNIQUE: Only one rule can match
   • FIRST: Return the first matching rule
   • PRIORITY: Return the highest priority match
   • ANY: All matches must have the same output
   • COLLECT: Return all matches
   • RULE_ORDER: Return matches in rule order
   • OUTPUT_ORDER: Return matches sorted by output

3. Input Columns: Define the input columns with:

   • Name
   • Data type (string, number, boolean, date)
   • Optional FEEL expression for transformation

4. Output Columns: Define the output columns with:

   • Name
   • Data type
   • Optional default value

5. Decision Rules: Define rules with:

   • Rule ID
   • Priority (for PRIORITY hit policy)
   • Input conditions (JSON format)
   • Output values (JSON format)
   • Optional annotation

Condition Syntax

The node supports FEEL-like expressions for conditions:

• Comparison: > 18, <= 100, = "US"
• Range: [18..65] (between 18 and 65)
• List: in ("US", "CA", "UK")
• Negation: != "EXCLUDED", not in ("A", "B")
• Any value: - (matches any value)

Example Conditions JSON

{
  "age": ">= 18",
  "country": "US",
  "score": "[70..100]",
  "category": "in (\"A\", \"B\", \"C\")",
  "status": "!= \"INACTIVE\""
}

Example Output JSON

{
  "discount": 0.15,
  "eligible": true,
  "tier": "GOLD"
}

Advanced Features

Options

• Strict Mode: Fail if no rules match (otherwise returns defaults)
• Include Metadata: Add metadata about matched rules to output
• Trace Execution: Include detailed execution trace for debugging

Aggregation (COLLECT Hit Policy)

When using COLLECT hit policy with aggregation:

• SUM: Sum of all numeric outputs
• COUNT: Count of matching rules
• MIN: Minimum numeric value
• MAX: Maximum numeric value

Development

# Install dependencies
npm install

# Build the node
npm run build

# Run in development mode (watch for changes)
npm run dev

# Run linter
npm run lint

# Format code
npm run format

Examples

Customer Discount Rules

{
  "inputColumns": [
    {"name": "customerType", "type": "string"},
    {"name": "orderTotal", "type": "number"},
    {"name": "loyaltyYears", "type": "number"}
  ],
  "outputColumns": [
    {"name": "discountPercent", "type": "number", "defaultValue": 0},
    {"name": "freeShipping", "type": "boolean", "defaultValue": false}
  ],
  "rules": [
    {
      "conditions": {
        "customerType": "PREMIUM",
        "orderTotal": ">= 100",
        "loyaltyYears": ">= 5"
      },
      "outputs": {
        "discountPercent": 20,
        "freeShipping": true
      }
    },
    {
      "conditions": {
        "customerType": "PREMIUM",
        "orderTotal": ">= 50"
      },
      "outputs": {
        "discountPercent": 15,
        "freeShipping": true
      }
    },
    {
      "conditions": {
        "customerType": "STANDARD",
        "orderTotal": ">= 100"
      },
      "outputs": {
        "discountPercent": 10,
        "freeShipping": true
      }
    }
  ]
}

License

MIT

Support

For bugs and feature requests, please create an issue on GitHub.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Acknowledgments

This node implements the DMN 1.3 specification for decision tables. For more information about DMN, visit the OMG DMN Specification.