Business Rule Task

Evaluates a DMN decision table and writes the output columns back as process variables. Combine with a Script Task or gateway conditions to branch on the decision result.

Properties

How It Works

1. Deploy your DMN XML via POST /api/v1/decisions
2. The decision’s id attribute becomes the Decision Ref
3. When a token reaches the business rule task, the engine evaluates the decision using current process variables as inputs
4. Output column values are written back as process variables with the same names as the output columns

XML Example

<bpmn:businessRuleTask id="classify_order" name="Classify Order">
  <bpmn:extensionElements>
    <conduit:decisionRef>order-classification</conduit:decisionRef>
  </bpmn:extensionElements>
  <bpmn:incoming>flow_to_classify</bpmn:incoming>
  <bpmn:outgoing>flow_to_route</bpmn:outgoing>
</bpmn:businessRuleTask>

Deploying a Decision

POST /api/v1/decisions
Content-Type: application/xml

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="https://www.omg.org/spec/DMN/20191111/MODEL/"
             id="order-decisions" name="Order Decisions"
             namespace="http://camunda.org/schema/1.0/dmn">
  <decision id="order-classification" name="Order Classification">
    <decisionTable hitPolicy="FIRST">
      <input id="amount_input" label="Amount">
        <inputExpression typeRef="number">
          <text>amount</text>
        </inputExpression>
      </input>
      <output id="tier_output" label="Tier" name="tier" typeRef="string"/>
      <rule id="rule1">
        <inputEntry><text>&gt; 1000</text></inputEntry>
        <outputEntry><text>"premium"</text></outputEntry>
      </rule>
      <rule id="rule2">
        <inputEntry><text></text></inputEntry>
        <outputEntry><text>"standard"</text></outputEntry>
      </rule>
    </decisionTable>
  </decision>
</definitions>

After this request, the variable tier is available to all subsequent elements in the instance.

See the Decision Tables docs for hit policies, FEEL input syntax, and full reference.

Pinning to a specific decision version

By default the engine evaluates the latest deployed version of the referenced decision. If a process needs to keep using a specific version even after a newer one is deployed, pin it with the version attribute:

<bpmn:businessRuleTask id="classify_order" name="Classify Order">
  <bpmn:extensionElements>
    <conduit:decisionRef version="3">order-classification</conduit:decisionRef>
  </bpmn:extensionElements>
  <bpmn:incoming>flow_to_classify</bpmn:incoming>
  <bpmn:outgoing>flow_to_route</bpmn:outgoing>
</bpmn:businessRuleTask>

Omit version (or set it to an empty string) to fall back to “latest”. Pinning is useful when you want to roll out a new decision version gradually — deploy the new version, then update individual processes to reference it, leaving older processes on the version they were tested against.