Exposing and consuming Things for a PoC in context of Digital Twins and Wald & Holz 4.0

This Repo contains a PoC to use WoT with digital twins. It's more a demonstration of the WoT technology then including it in the Wald & Holz Infrastracture. It was developed in the context of a semester work to show capabilities of WoT and Web semanic in Digital Twins and Digital Twin infrastructure.

Architecture

Above you can see the Archtiecture. The whole thing consists of two Eclipse thingweb Servients connected with each other. The right Servient takes on the role of a server and the left one takes on the role of a client. Above all we have the Graphdb which contains the fml4.0 and ml4.0 ontology. It's used to ensure a semantic understanding among multiple servients. The Servient is not directly integrated in the Client, instead it's an independent project to demonstrate how Thing Descriptions can be secure with a TPM. You can find it here

Server

The Server is exposing a thing which in this case represents a Digital Twin connecting to the W&H4.0 Infrastructure. In this case the Digital Twin is a Raspberry Pi with a PIR motion Sensor and a RPi camera. For additional security there is a Trusted Platform Module 2.0 implemented.

Client

The Client Servient can be initiaded on a client device and is capable of consuming the W&H4.0 DT. It can then start a communication with the W&H4.0 DT. It can read Properties (location, status, last action), it can trigger some actions (take a picture) and listen to events (motion sensor got triggered).

GraphDB

To run the docker GraphDB Free you have to apply for the free version on the offical website. Follow the official Repo instructions here.
Then import the two ontologies fml40 and ml40 from here and here. On this site you can find information on how to setup a DB Repo and how to import the ontologies.

query

The following query is needed to get the desired device:

PREFIX ml40: <http://www.kwh-ontology/ml40#>
PREFIX fml40: <http://www.kwh-ontology/fml40#>
PREFIX ssn: <http://purl.oclc.org/NET/ssnx/ssn#>
PREFIX td: <http://mywotontology#>
select ?endpoint ?feature where { 
	?s a ml40:Device.
    ?sensor a ssn:SensingDevice .
    ?s ml40:hasSensor ?sensor.
    ?s fml40:Endpoint ?endpoint .
    ?feature a fml40:ObservingJob .
    ?s fml40:hasFeature ?feature   
    
} limit 100

Thing Description

In order for the Server to expose the Thing it needs some Thing Description(TD). You can inspect the used TD below:

{
  "@context": [
    "https://www.w3.org/2019/wot/td/v1",
    { "@language": "en" }],
  "@type": "http://purl.oclc.org/NET/ssnx/ssn#SensingDevice",
  id: "kwh-thingID-1",
  title: "kwh-thing",
  titles: {
    "en": "kwh-thing",
    "de": "kwh-ding",
    "it": "kwh-cosa"
  },
  description: "This is an experimental kwh thing to showcase the possibilities of WoT",
  descriptions: {
    "en": "This is an experimental kwh thing to showcase the          possibilities of WoT",
    "de": "Das ist ein experimentelles Ding mit welchem die Möglichkeiten des WoT gezeigt werden können",
    "it": "Questa è una cosa sperimentale con cui si possono mostrare le possibilità di WoT"
  },
  support: "git://github.com/eclipse/thingweb.node-wot.git",
  securityDefinitions: {
    "": {
        "scheme": ""
    }
  },
  security: "",
  properties: {
    lastSnapshot: {
      description: "returns the last image taken by action takePhoto",
      forms: [{
          contentType: "image/png"
      }]
    },
    movement: {
      title: "Counting the number of movements detected",
      description: "This kwh-thing includes a pir motion sensor. This field shows the number of movements which got detected",
      unit: "",
      type: "integer",
      observable: true,
      readOnly: true
    }
  },
  actions: {
    takePhoto: {
      "@type": "http://www.kwh-ontology/fml40#feature",
      title: "Takes img with the mounted camera",
      description: "On this kwh-thing there is a camera attached and if invoked will take an image",
          input: {
              type: "string"
          },
          forms: [{
              op: "invokeaction",
              contentType: "application/json",
          }],
    }
  },
  events: {
    movementDetected: {
      "@type": "http://www.kwh-ontology/fml40#ObservingJob",
      title: "Trespassing alarm",
      description: "Event when subscribed notifies if movement gets detected from the PIR sensor",
      data: {
          unit: "",
          type: "string"
      }
    }
  },
}

The TD is represents an invented Thing and is because of demonstration purposes fairly simple. It's based on a camera trap which could be used in a forest like environment. But it might be something more sophisticated like a Digital Twin. It contains properties such as the location of the device and how many times an animal triggered the motion sensor. As an ActionAffordance it's using a camera to trigger to do a snapshot of the environment. For

Development Setup

VS Code RemoteDevelopment
follwing this blogpost

• allow camera module;

• allow gpio read pins

• enable ssh

• change sudo $PATH VIM ~./bash and add :/home/pi/.nvm/versions/node/v14.15.0/bin