Event Types

Event types define custom OPC UA events that nodes can emit. They are modelled as ObjectType subclasses of ua:BaseEventType and can carry custom fields.

Event type definition
eventTypes:
  - browseName: TemperatureAlarmType
    subtypeOf: ua:AlarmConditionType
    description: Fired when a temperature sensor exceeds its threshold.
    properties:
      - browseName: ThresholdValue
        dataType: ua:Double
        description: The configured threshold that was exceeded.
      - browseName: MeasuredValue
        dataType: ua:Double
        description: The actual measured temperature at the time of the alarm.

Fields

Event types support the same fields as objectTypes:

Field	Description
`browseName`	Name of the event type (PascalCase, suffix `Type` by convention)
`subtypeOf`	Parent event type (default: `ua:BaseEventType`)
`properties`	Custom fields carried by the event
`components`	Sub-objects attached to the event
`description`	Human-readable description of when the event fires
`isAbstract`	`true` for base event types not emitted directly

Common base types

Base type	Use for
`ua:BaseEventType`	Generic custom events
`ua:AuditEventType`	Security audit trail events
`ua:ConditionType`	Stateful condition events
`ua:AlarmConditionType`	Alarm events with active/inactive states
`ua:DiscreteAlarmType`	Alarms triggered by discrete state changes
`ua:LimitAlarmType`	Alarms triggered by high/low/high-high/low-low limits

Linking event types to nodes: `generatedEvents`

Declare which event types an object or object type can emit using generatedEvents:

Linking generatedEvents to an object type
objectTypes:
  - browseName: TemperatureSensorType
    components:
      - browseName: Temperature
        dataType: ua:Double
        modellingRule: Mandatory
    generatedEvents:
      - TemperatureAlarmType

This emits a GeneratesEvent reference in the NodeSet, informing OPC UA clients which event types they should subscribe to on instances of this type.

📄 Full working example — event-types.model.yaml

event-types.model.yaml
# yaml-language-server: $schema=../../../../schemas/nodeset2.schema.json
#
# Living documentation example for: s45_event-types.md
# Validate: opcua-modeler generate --input event-types.model.yaml

namespaceUri: http://example.com/doc/event-types/
version: 1.0.0

eventTypes:
  - browseName: TemperatureAlarmType
    subtypeOf: ua:AlarmConditionType
    description: Fired when a temperature sensor exceeds its threshold.
    properties:
      - browseName: ThresholdValue
        dataType: ua:Double
        description: The configured threshold that was exceeded.
      - browseName: MeasuredValue
        dataType: ua:Double
        description: The actual measured temperature at the time of the alarm.

objectTypes:
  - browseName: TemperatureSensorType
    components:
      - browseName: Temperature
        dataType: ua:Double
        modellingRule: Mandatory
    generatedEvents:
      - TemperatureAlarmType

# ── Full standalone example ────────────────────────────────────────────────────
# namespaceUri: http://example.com/sensor/
# version: 1.0.0

# eventTypes:
#   - browseName: SensorFaultType
#     subtypeOf: ua:BaseEventType
#     description: |
#       Emitted when a sensor self-diagnosis detects a hardware fault.
#     properties:
#       - browseName: FaultCode
#         dataType: ua:UInt32
#       - browseName: FaultDescription
#         dataType: ua:LocalizedText

# objectTypes:
#   - browseName: SmartSensorType
#     generatedEvents:
#       - SensorFaultType
#     components:
#       - browseName: Status
#         dataType: ua:Byte

📄 Generated NodeSet2.xml — event-types.model.Nodeset2.xml

event-types.model.Nodeset2.xml
<?xml version="1.0"?>
<UANodeSet xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:uax="http://opcfoundation.org/UA/2008/02/Types.xsd" xmlns="http://opcfoundation.org/UA/2011/03/UANodeSet.xsd" xmlns:ns1="http://example.com/doc/event-types/Type.xsd">
    <NamespaceUris>
        <Uri>http://example.com/doc/event-types/</Uri>
    </NamespaceUris>
    <Models>
        <Model ModelUri="http://example.com/doc/event-types/" Version="1.0.0" PublicationDate="2026-05-26T09:24:00.000Z">
            <RequiredModel ModelUri="http://opcfoundation.org/UA/" Version="1.05.06" PublicationDate="2025-11-08T00:00:00.000Z"/>
        </Model>
    </Models>
    <Aliases>
        <Alias Alias="Double">i=11</Alias>
        <Alias Alias="GeneratesEvent">i=41</Alias>
        <Alias Alias="HasComponent">i=47</Alias>
        <Alias Alias="HasModellingRule">i=37</Alias>
        <Alias Alias="HasProperty">i=46</Alias>
        <Alias Alias="HasSubtype">i=45</Alias>
        <Alias Alias="HasTypeDefinition">i=40</Alias>
    </Aliases>
<!--ReferenceTypes-->
<!--ObjectTypes-->
<!--ObjectType - 1:TemperatureAlarmType {{{{ -->
    <UAObjectType NodeId="ns=1;i=1000" BrowseName="1:TemperatureAlarmType">
        <DisplayName>TemperatureAlarmType</DisplayName>
        <Description>Fired when a temperature sensor exceeds its threshold.</Description>
        <References>
            <Reference ReferenceType="HasSubtype" IsForward="false">i=2915</Reference>
            <Reference ReferenceType="HasProperty">ns=1;i=1001</Reference>
            <Reference ReferenceType="HasProperty">ns=1;i=1002</Reference>
        </References>
    </UAObjectType>
    <UAVariable NodeId="ns=1;i=1001" BrowseName="1:ThresholdValue" ParentNodeId="ns=1;i=1000" AccessLevel="3" DataType="Double">
        <DisplayName>ThresholdValue</DisplayName>
        <Description>The configured threshold that was exceeded.</Description>
        <References>
            <Reference ReferenceType="HasTypeDefinition">i=68</Reference>
            <Reference ReferenceType="HasModellingRule">i=78</Reference>
        </References>
    </UAVariable>
    <UAVariable NodeId="ns=1;i=1002" BrowseName="1:MeasuredValue" ParentNodeId="ns=1;i=1000" AccessLevel="3" DataType="Double">
        <DisplayName>MeasuredValue</DisplayName>
        <Description>The actual measured temperature at the time of the alarm.</Description>
        <References>
            <Reference ReferenceType="HasTypeDefinition">i=68</Reference>
            <Reference ReferenceType="HasModellingRule">i=78</Reference>
        </References>
    </UAVariable>
<!--ObjectType - 1:TemperatureAlarmType }}}}-->
<!--ObjectType - 1:TemperatureSensorType {{{{ -->
    <UAObjectType NodeId="ns=1;i=1003" BrowseName="1:TemperatureSensorType">
        <DisplayName>TemperatureSensorType</DisplayName>
        <References>
            <Reference ReferenceType="HasSubtype" IsForward="false">i=58</Reference>
            <Reference ReferenceType="GeneratesEvent">ns=1;i=1000</Reference>
            <Reference ReferenceType="HasComponent">ns=1;i=1004</Reference>
        </References>
    </UAObjectType>
    <UAVariable NodeId="ns=1;i=1004" BrowseName="1:Temperature" ParentNodeId="ns=1;i=1003" AccessLevel="3" DataType="Double">
        <DisplayName>Temperature</DisplayName>
        <References>
            <Reference ReferenceType="HasTypeDefinition">i=63</Reference>
            <Reference ReferenceType="HasModellingRule">i=78</Reference>
        </References>
    </UAVariable>
<!--ObjectType - 1:TemperatureSensorType }}}}-->
<!--VariableTypes-->
<!--Other Nodes-->
</UANodeSet>

Fields​

Common base types​

Linking event types to nodes: generatedEvents​

Fields

Common base types

Linking event types to nodes: `generatedEvents`