{
	"$id": "validate_Msg",
	"$schema": "http://json-schema.org/draft-07/schema#",
	"type" : "object",
	"required" : ["id", "referer", "dt"],
	"properties" : {
		"id" : { "type" : "string"},
		"referer" : { "type" : "string"},
		"dt" : { "type" : "string" }
	}
}

{
	"$id": "validate_Msg_msg",
	"$schema": "http://json-schema.org/draft-07/schema#",
	"type" : "object",
	"required" : ["_msg"]
}

{
	"$id": "validate_MsgAck",
	"$schema": "http://json-schema.org/draft-07/schema#",
	"type" : "object",
	"required" : ["ack"],
	"properties" : {
		"ack" : {
			"type" : "object",
			"required" : ["ok"],
			"properties" : {
				"ok" : { "type" : "boolean" }
			}
		}
	}
}

TODO: add optional expired property