In this Internet of Things (IoT) era, our everyday objects have evolved into the so-called cyber-physical systems (CPS). The use and deployment of CPS has especially penetrated the industry, giving rise to the Industry 4.0 or Industrial IoT (IIoT). Typically, architectures in IIoT environments are distributed and asynchronous, communication being guided by events such as the publication of (and corresponding subscription to) messages. While these architectures have some clear advantages (such as scalability and flexibility), they also raise interoperability challenges among the agents in the network. Indeed, the knowledge about the message content and its categorization (topics) gets diluted, leading to consistency problems, potential losses of information and complex processing requirements on the subscriber side to try to understand the received messages. In this paper, we present our proposal relying on \emph{AsyncAPI} to automate the design and implementation of these architectures using model-based techniques for the generation of (part of) event-driven infrastructures. The prototype that implements this proposal as an open-source project is available at https://github.com/SOM-Research/asyncapi-toolkit

1. A model-based approach for
developing event-driven
architectures with AsyncAPI
Abel Gómez1, Markel Iglesias-Urkia2, Aitor Urbieta2, Jordi Cabot1,3
1Universitat Oberta de Catalunya, 2Ikerlan, 3ICREA
MODELS conference – April 22, 2020

2. Subscribe!
Publish!
Broker

4. An illustrative example

5. An illustrative example

6. Iotbox/box1/monitor
An illustrative example
{
"id": "Line A",
"presses":[
{
"id": "Press A1",
"ts": "2020-05-11T18:01:06.158Z",
"value": 10.0
},{
"id": "Press A2",
"ts": "2020-05-11T18:01:06.329Z",
"value": 15.5
}
]
}

7. An illustrative example

8. An illustrative example
Iotbox/box1/monitoring
{
"id": "Line A",
"Press A1": {
"ts": "2020-05-11T18:01:06.158Z",
"value": 10.0
},
"Press A2“: {
"ts": "2020-05-11T18:01:06.329Z",
"value": 15.5
}
]
}
Iotbox/box1/monitor
{
"id": "Line A",
"presses":[
{
"id": "Press A1",
"ts": "2020-05-11T18:01:06.158Z",
"value": 10.0
},{
"id": "Press A2",
"ts": "2020-05-11T18:01:06.329Z",
"value": 15.5
}
]
}

9. It is difficult to maintain consistency:
• Deviations in the topics:
• Lost messages
• Deviations in the message format:
• Information loss
• Runtime problems
Message-driven APIs

11. {
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

12. {
"asyncapi": "2.0.0",
"info": { … },
"servers": {
…
},
"channels": {
…
},
"components": {
…
}
}
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

13. "info": {
"title": "IoTBox API",
"version": "1.0.0"
},
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

14. "servers": {
"production": {
"protocol": "mqtt",
"url": "example.com:1883"
}
},
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

15. "channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": ...,
"schema": { "type": "string" }
}
},
"publish": { ... },
"subscribe": { ... }
}
},
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

16. "publish": {
"operationId": "publishStatus",
"message": {
"$ref": "#/components/messages/statusMessage"
}
},
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

17. "components": {
"messages": {
…
},
"schemas": {
…
}
}
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

18. "messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": {
"$ref": "#/components/schemas/lineInfo"
}
}
},
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

19. "lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": {
"$ref": "#/components/schemas/pressInfo“
}
}
}
},
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

20. "pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
{
"asyncapi": "2.0.0",
"info": { "title": "IoTBox API", "version": "1.0.0”},
"servers": {
"production": { "protocol": "mqtt", "url": "example.com:1883" }
},
"channels": {
"iotbox/{id}/monitor": {
"parameters": {
"id": {
"description": "The ID of the IoTBox",
"schema": { "type": "string" }
}
},
"publish": {
"operationId": "publishStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
},
"subscribe": {
"operationId": "subscribeStatus",
"message": { "$ref": "#/components/messages/statusMessage" }
}
}
},
"components": {
"messages": {
"statusMessage": {
"description": "Status of a given subsystem",
"payload": { "$ref": "#/components/schemas/lineInfo" }
}
},
"schemas": {
"lineInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the subsystem"
},
"presses": {
"type": "array",
"description": "Info of presses in this subsystem",
"items": { "$ref": "#/components/schemas/pressInfo" }
}
}
},
"pressInfo": {
"type": "object",
"properties": {
"id": {
"type": "string",
"description": "Identifier of the press"
},
"ts": {
"type": "string",
"title": "Timestamp"
},
"value": {
"type": "number",
"description": "Pressure of the press in Pascals"
}
}
}
}
}
}

22. AsyncAPI toolkit
A model-based approach for developing
event-driven architectures with AsyncAPI

23. AsyncAPI toolkit

24. A grammar for the AsyncAPI specification

25. AsyncAPI:
{AsyncAPI} '{‘ (
( '"asyncapi"' ':' version=VersionNumber ','? )
& ( '"info"' ':' info=Info ','? )
& ( '"servers"' ':' '{' servers+=Server (',' servers+=Server)* '}' ','? )?
& ( '"channels"' ':' '{' channels+=Channel (',' channels+=Channel)* '}' ','? )?
& ( '"components"' ':' components=Components ','? )?
) '}';
Info:
{Info} '{' (
( '"title"' ':' title=AnyString ','? )
& ( '"version"' ':' version=AnyString ','? )
& ( '"description"' ':' description=AnyString ','? )?
& ( '"termsOfService"' ':' termsOfService=AnyString ','? )?
& ( '"contact"' ':' contact=Contact ','? )?
& ( '"license"' ':' license=License ','? )?
) '}';
A grammar for the AsyncAPI specification

26. A metamodel for the AsyncAPI specification

27. Defining an event-driven architecture

28. Equivalent API model

29. The generated code

30. The generated code
package main;
import java.time.Instant;
import iotbox._id_.monitor.PublishStatus;
import iotbox._id_.monitor.PublishStatus.PublishStatusParams;
import schemas.LineInfo;
import schemas.PressInfo;
public class Publish {
public static void main(String[] args) throws Exception {
LineInfo payload = LineInfo.newBuilder()
.withId("Line A")
.addToPresses(
PressInfo.newBuilder()
.withId("Press A1")
.withTimestamp(Instant.now().toString())
.withValue(10.0)
.build()
)
.addToPresses(
PressInfo.newBuilder()
.withId("Press A2")
.withTimestamp(Instant.now().toString())
.withValue(15.5)
.build()
)
.build();
PublishStatusParams params = PublishStatusParams.create().withId("box1");
PublishStatus.publish(payload, params);
}
}
{
"id": "Line A",
"presses": [
{
"id": "Press A1",
"ts": "2020-05-11T18:01:06.158Z",
"value": 10.0
},{
"id": "Press A2",
"ts": "2020-05-11T18:01:06.329Z",
"value": 15.5
}
]
}

31. • With AsyncAPI Toolkit, an AsyncAPI specification is the singlesource
of truthwhen designing and running an event-driven architecture.
• The AsyncAPI Toolkit leverages model-based techniques for:
• lower development and deployment time;
• better code quality;
• increased maintanability
• better requirements management;
• better documentation.
Summary and conclusions
We see AsyncAPI Toolkit as a toolkit able to support most
phasesof the development cycle, from requirementsto
code-generation to —in the future— testing.
—Ikerlan

32. UOCresearch
@UOC_research
https://github.com/SOM-Research/asyncapi-toolkit
agomezlla@uoc.edu