BaSyx / Documentation / Components / AAS Server / Features / Hierarchical MQTT

Hierarchical MQTT Eventing

User Story & Use Case

As AAS Components user

I want hierarchical MQTT topics in the AAS Server Component

so that I can subscribe precisely to the topics of interest without having to filter on client side

MQTT supports hierarchical topics with wildcard subscription support. For example, if the topics a/b/x and a/b/y exist, subscribing to a/b/+ subscribes to all events broadcasted on both topics.

Please note, that this feature can not be combined with lambda properties due to them being only updated on query.

Feature Overview

The following hierarchical topics with their respective payloads are implemented:

• aas-repository/<repo-id>/shells/created
  • Payload: Complete AAS (without ConceptDictionaries)
• aas-repository/<repo-id>/shells/deleted
  • • Payload: Complete AAS (old, without ConceptDictionaries)
• aas-repository/<repo-id>/shells/updated
  • Payload: Complete AAS (without ConceptDictionaries)

• aas-repository/<repo-id>/shells/<encoded-aas-identifier>/submodels/created
  • Payload: Submodels without SMEs
• aas-repository/<repo-id>/shells/<encoded-aas-identifier>/submodels/deleted
  • Payload: Submodels without SMEs
• aas-repository/<repo-id>/shells/<encoded-aas-identifier>/submodels/updated
  • Payload: Submodels without SMEs

• aas-repository/<repo-id>/shells/<encoded-aas-identifier>/submodels/<encoded-sm-identifier>/submodelElements/<idShortPath>/created
  • Payload: SME without value (or value-equivalent)
• aas-repository/<repo-id>/shells/<encoded-aas-identifier>/submodels/<encoded-sm-identifier>/submodelElements/<idShortPath>/deleted
  • Payload: old SME without value (or value-equivalent)
• aas-repository/<repo-id>/shells/<encoded-aas-identifier>/submodels/<encoded-sm-identifier>/submodelElements/<idShortPath>/updated
  • Payload: SME without value (or value-equivalent)
• aas-repository/<repo-id>/shells/<encoded-aas-identifier>/submodels/<encoded-sm-identifier>/submodelElements/<idShortPath>/value
  • SME value, if not specified otherwise via qualifier

For AAS/SM-Identifier encoding, Base64URL encoding and URL encoding are available.

Feature Configuration

The feature can be configured in the aas.properties file by setting aas.events = MQTTV2 for Base64URL encoding or aas.events = MQTTV2_SIMPLE_ENCODING for URL encoding. Additionally, the repo id needs to be configured via aas.id = <repo-id>.

An example configuration for this feature could be:

aas.events = MQTTV2
aas.id = product-aas-repo

The MQTT broker connectivity is configured via mqtt.properties

Additional to the overall event configuration, the payload send on the ../value topic for updating a SubmodelElement's value can be tailored. For SubmodelElements containing huge values like Blobs, it may be sensible to disable sending their value's content. If this is the case, a qualifier with type emptyValueUpdateEvent and value set to true will configure empty value updates for the specific SubmodelElement (cf. ObservableSubmodelAPIV2Helper).