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, RULEORDER, and OUTPUTORDER
• 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

!Input conditions for an example rule

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

| Rule | Age | Country | Discount | Eligible |
|——|—–|———|———-|———-|
| 1 | >= 65 | US | 0.2 | true |
| 2 | >= 18 | US | 0.1 | true |
| 3 | < 18 | - | 0 | false |

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.