schema.json

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "http://shone.com/anorak.json",
  "title": "Anorak",
  "description": "Portable Realtime Maritime Navigational Data Protocol",
  "oneOf": [
    { "$ref": "#subscribeMessage" },
    { "$ref": "#unsubscribeMessage" },
    { "$ref": "#getMessage" },
    { "$ref": "#deltaMessage" },
    { "$ref": "#fullMessage" }
  ],
  "definitions": {
    "mmsi": {
      "$id": "#mmsi",
      "description": "The vessel unique identifier",
      "type": "string"
    },
    "source": {
      "$id": "#source",
      "description": "One apparatus measuring facts on a vessel",
      "type": "string",
      "enum": [
        "gps",
        "ecdis",
        "radar",
        "compas",
        "dopplerspeedlog",
        "depthsounder",
        "ais",
        "autopilot",
        "bnwas",
        "steeringgear"
      ]
    },
    "singleDelta": {
      "$id": "#singleDelta",
      "description": "One single delta message",
      "type": "object"
    },
    "subscribeMessage": {
      "$id": "#subscribeMessage",
      "description": "Request to start receiving delta updates",
      "type": "object",
      "properties": {
        "op": {
          "type": "string",
          "const": "subscribe"
        },
        "mmsi": { "$ref": "#mmsi" },
        "source": { "$ref": "#source" }
      }
    },
    "unsubscribeMessage": {
      "$id": "#unsubscribeMessage",
      "description": "Request to stop receiving delta updates",
      "type": "object",
      "properties": {
        "op": {
          "type": "string",
          "const": "unsubscribe"
        },
        "mmsi": { "$ref": "#mmsi" },
        "source": { "$ref": "#source" }
      }
    },
    "getMessage": {
      "$id": "#getMessage",
      "description": "Request to get a full state update",
      "type": "object",
      "properties": {
        "op": {
          "type": "string",
          "const": "get"
        },
        "mmsi": { "$ref": "#mmsi" },
        "source": { "$ref": "#source" }
      }
    },
    "deltaMessage": {
      "$id": "#deltaMessage",
      "type": "object",
      "description": "A delta update",
      "properties": {
        "op": {
          "type": "string",
          "const": "delta"
        },
        "mmsi": { "$ref": "#mmsi" },
        "source": { "$ref": "#source" },
        "delta": {
          "type": "array",
          "minItems": 1,
          "items": { "$ref": "#singleDelta" }
        }
      }
    },
    "fullMessage": {
      "$id": "#fullMessage",
      "description": "A full state update",
      "type": "object",
      "properties": {
        "op": {
          "type": "string",
          "const": "full",
          "mmsi": { "$ref": "#mmsi" },
          "source": { "$ref": "#source" },
          "full": {
            "type": "array",
            "minItems": 1,
            "items": { "$ref": "#singleDelta" }
          }
        }
      }
    }
  }
}

That's good. What is the purpose of get vs full and delta though ?

Get is to request a full state. Full is the response. Subscribe is to request to start receiving delta updates, and delta is one of those updates.

I updated the gist to comment it out.

Ok thanks @baptistemanson

Updated with the new sources @azouz provided.

Corrected the typo on compass.

How would the full state work exactly ? From what I see it is an array of delta updates. Is this easily streamable ? I think one of the key points you mentioned during the meeting @baptistemanson was the ability to stream the full state instead of having to parse a large json object as is the case with SignalK for instance. In this case, would we split the full state in multiple messages to stream by batches of N delta updates ? If so should we add a pagination parameter ?