Digital Twins as part of an open IoT platform

16.04.2020

agenda

Digital Twins
Eclipse Ditto
Ditto + TTN
Hands-on
Wrap up

Digital Twins

digital representation of real physical devices
act as broker for communicating with assets
also: representation of processes or services
applicable for both industrial and consumer-centric IoT scenarios

Eclipse Ditto

… where IoT devices and their Digital Twins get together

in context

Ditto as
Digital Twin
"middleware"

turn device data into APIs

{
  "thingId": "io.foo:car1",
  "policyId": "io.foo:car1",
  "attributes": {
    "manufacturer": "Foo corp",
    "productionData": {
      "serialNo": 4711
    }
  },
  "features": {
    "temperature": {
      "properties": {
        "value": 23.42
      }
    }
  }
}

JSON repr. of a Thing

GET/PUT/DELETE /api/2/things/io.foo:car1
 /api/2/things/io.foo:car1/thingId
 /api/2/things/io.foo:car1/policyId
 /api/2/things/io.foo:car1/attributes
 /api/2/things/io.foo:car1/attributes/manufacturer
 /api/2/things/io.foo:car1/attributes/productionData
 /api/2/things/io.foo:car1/attributes/productionData/serialNo


 /api/2/things/io.foo:car1/features
 /api/2/things/io.foo:car1/features/temperature
 /api/2/things/io.foo:car1/features/temperature/properties
 /api/2/things/io.foo:car1/features/temperature/properties/value

→ docs

persistence of device state

devices are not always connected to the net
applications always need to be able to access their data
twin vs. live access on API level

authorization

Ditto contains a built-in authorization mechanism (Policies)
every API call is authorized

{
    "policyId": "io.foo:car1-policy",
    "entries": {
      "owner": {
        "subjects": {
          "nginx:admin": {
            "type": "nginx basic auth user"
          }
        },
        "resources": {
          "thing:/": {
            "grant": ["READ","WRITE"],
            "revoke": []
          },
          "thing:/features/firmware": {
            "grant": [],
            "revoke": ["WRITE"]
          },
          "policy:/": {
            "grant": ["READ","WRITE"],
            "revoke": []
          }
        }
      }
    }
  }

→ docs

search

you must not
Ditto has you covered

GET /api/2/search/things
  ?filter=like(attributes/manufacturer,"Foo*")

GET /api/2/search/things
  ?filter=and(
    exists(attributes/manufacturer),
    gt(features/temperature/properties/value,23.0)
  )
  &namespaces=io.foo
  &option=sort(-_modified,-attributes/manufacturer)
  &fields=thingId,attributes/manufacturer,_modified

search for arbitrary data with RQL query
Ditto again ensures authorization
apply field projection over the results
don't worry about indexing

→ docs

get notified about changes

notification via various channels: WebSocket, SSE, MQTT, AMQP, Kafka, HTTP hook
server side filtering via RQL (same as in search)

var ws = new WebSocket("ws://ditto:ditto@localhost:80/ws/2");
ws.onopen = function(w) {
  w.send('START-SEND-EVENTS?filter=gt(features/temperature/properties/value,25)');
};
ws.onmessage = function(msg) {
  console.log('received: ' + msg.data);
};

example of WebSocket browser API

→ docs

payload normalization

devices send data in various formats
Ditto provides structured APIs of things (attributes, features)
devices don't need to be aware of Ditto

incoming and outgoing data can be transformed

nonfunctional

modular architecture of Ditto services
horizontal scalability of each Ditto service
runtime dependency to MongoDB
included monitoring (JVM metrics, roundtrips, MongoDB)
codebase written in: Java

Eclipse Ditto +

benefit from each other

TTN solving low cost, wide range connectivity of devices
Eclipse Ditto providing APIs for IoT (backend-, web-, mobile-) applications
both provide free/community variants
both provide commercial services

integration variants

using TTN's HTTP integration

using TTN's MQTT broker

Digital Twins as part of an open IoT platform

16.04.2020

agenda

Digital Twins

Eclipse Ditto

… where IoT devices and their Digital Twins get together

in context

turn device data into APIs

persistence of device state

authorization

search

get notified about changes

payload normalization

nonfunctional

Eclipse Ditto +

benefit from each other

integration variants

using TTN's HTTP integration

using TTN's MQTT broker

* used now for the hands-on part

hands-on time!

Step-by-step blogpost

Wrap up

thanks to The Things Network for organising this virtual conference