Change @context of Thing Descriptions

[benfrancis]

Blocks: #2802

Once the Thing Descriptions exposed by the gateway are W3C compliant, we should update the @context member to include the string https://www.w3.org/2019/wot/td/v1 to reflect that.

Open questions:

1. We still want to be able to provide https://webthings.io/schemas/ as a context in order to add semantic annotations from the WebThings capability schemas. Does this mean we'll need to add a prefix to all of those annotations? e.g.

{
  "@context": ["https://www.w3.org/2019/wot/td/v1", {"wt": "https://webthings.io/schemas/"} ],
  "@type": ["wt:Light", "wt:OnOffSwitch"],
  "id": "https://mywebthingserver.com/things/lamp",
  "title": "My Lamp",
  "description": "A web connected lamp",
  "properties": {
    "on": {
      "@type": "wt:OnOffProperty",
    },
    "brightness" : {
      "@type": "wt:BrightnessProperty",
    }
  },
  "actions": {
    "fade": {
      "@type": "wt:FadeAction"
    }
  },
  "events": {
    "overheated": {
      "@type": "wt:OverheatedEvent"
    }
  }
}

Note: This should only be done once we've made all the other changes to make Thing Descriptions W3C compliant.

See WebThingsIO/api#157 for some past discussion

[benfrancis]

1. Does this mean we'll need to add a prefix to all of those annotations?

I think I'm right in saying that as long as there aren't collisions in the annotation names, it would be possible to add the WebThings schema annotations without a prefix. E.g.

{
  "@context": [
    "https://www.w3.org/2019/wot/td/v1",
    "https://webthings.io/schemas/" 
  ],
  "@type": ["Light", "OnOffSwitch"],
  "id": "https://mywebthingserver.com/things/lamp",
  "title": "My Lamp",
  "description": "A web connected lamp",
  "properties": {
    "on": {
      "@type": "OnOffProperty",
    },
    "brightness" : {
      "@type": "BrightnessProperty",
    }
  },
  "actions": {
    "fade": {
      "@type": "FadeAction"
    }
  },
  "events": {
    "overheated": {
      "@type": "OverheatedEvent"
    }
  }
}

[benfrancis]

Note: The context URL for TD 1.1 has now been specified as https://www.w3.org/2022/wot/td/v1.1, which is what we should use.

[benfrancis]

See also:

• Change default `@context' of devices gateway-addon-node#121
• Change default `@context' of devices gateway-addon-python#93