Communication Protocol

Communication with MemoNodes can be done via regular HTTP POST requests, using the JSON-RPC protocol. This is a simple and readable protocol, using JSON to format requests and responses. JSON (JavaScript Object Notation) is a lightweight, flexible data-interchange format, easy to read for humans to read and write, and for machines to parse and generate.

JSON-RPC

JSON-RPC is implemented in two ways:

• Asynchronous
  Requester performs an HTTP POST request to a MemoNodes instance. When MemoNodes has completed the action, it calls back the requester at the specified callback URL, containing the response.

Note that only JSON-RPC 2.0 is supported. In JSON-RPC 2.0, method parameters are defined as an object with named parameters, unlike JSON-RPC 1.0 where method parameters are defined as an array with unnamed parameters, which is much more ambiguous.

Asynchronous communication

Requester (which can be an agent or a human) performs a request to MemoNodes.

http://myserver.com/memo/Y

{ 
  "id": 1,
  "method": "add_domain",
  "params": {
    "domain": "Questionnaire", 
    "namespace": "http://questionnaire.com/domain/ns:questionnaire"
  },
  "callback": {
    "url": "http://myserver.com/agentX",
    "method": "addCallback"
  }
}

{
  "id": 1,
  "result": null,
  "error": null
}

As soon as MemoNodes has executed the task from the queue, it returns the result via a new request, adressing the callback url and method of agent X:

http://myserver.com/agent/X

{
  "id": 1,
  "method": "addCallback",
  "params": {
    "result: "domain(Questionnaire, http://questionnaire.com/domain/ns:questionnaire)",
    "error": null
  }
}

{
  "id": 1,
  "result": null,
  "error": null
}

Documentation

Documentation on the JSON-RPC protocol can be found via the following links:

• http://www.json.org
• http://json-rpc.org
• http://jsonrpc.org
• http://en.wikipedia.org/wiki/Json
• http://en.wikipedia.org/wiki/JSON_RPC