7.3.4.7.2 MessageType mapping
<MqttMessageType> Topic levels exist for each MessageType defined in 7.2.2. Additional information like requirements for RETAIN for each Topic level is provided in Table 204. The handling of RETAIN messages is defined in 7.3.4.8.
The requirements for topic access permissions are defined in Table 205.
| MessageType | MqttMessageType | RETAIN | Required | Specification Reference |
|---|---|---|---|---|
| DataSetMessage | data | False | Yes | Defined in 7.3.4.7.3. A system specific Topic may be used instead The RETAIN false is the default setting. |
| DataSetMetaData | metadata | True | Yes | Defined in 7.3.4.7.4. A system specific Topic may be used instead. |
| ApplicationDescription | application | True | No | Defined in 7.3.4.7.5. |
| ServerEndpoints | endpoints | True | No | Defined in 7.3.4.7.6. |
| Status | status | True | Yes | Defined in 7.3.4.7.7. |
| PubSubConnection | connection | True | Yes | Defined in 7.3.4.7.8. |
| ActionRequest | action-request | False | Yes | Defined in 7.3.4.7.9. A system specific Topic may be used instead |
| ActionResponse | action-response | False | No | Defined in 7.3.4.7.10. The ActionResponse topic can be specified by the Requestor. |
| ActionMetaData | action-metadata | True | Yes | Defined in 7.3.4.7.12. A system specific Topic may be used instead |
| ActionResponder | action-responder | True | Yes | Defined in 7.3.4.7.11. |
| MqttMessageType | Publisher | Subscriber | Description |
|---|---|---|---|
| data | Write | Read | Variables and Events from an OPC UA applications acting as Publisher have RolePermissions. Such RolePermissions have no affect after DataSetMessages are sent to the MQTT broker. It is therefore recommended to synchronize Roles used to configure read permissions to the topics with the Roles required to access the information in the Publisher OPC UA application. |
| metadata | Write | Read | |
| application | Write | Read | The information published with this message type is similar to discovery information provided with OPC UA Client Server discovery. This information is normally not restricted for read access. |
| endpoints | Write | Read | |
| status | Write | Read | |
| connection | Write | Read | |
| action-request | Read | Write | Publisher is the Responder and Subscriber is the Requestor. The topic with message type action-request is defined by the Responder with its PublisherId but the Requestors must have write permission to the topic. Only the Responder should be able to read from the topic. |
| action-response | Write | Read | Publisher is the Responder and Subscriber is the Requestor. If the Responder specifies the response topic it must be ensured that the Responder has Write access to this topic. The Requestor should either use unique random correlation data or should use a private response topic where only the Requestor is able to read from. |
| action-metadata | Write | Read | |
| action-responder | Write | Read |