# Get the JSON body of a REST request that create the relationship.
	private fun to_rest: JsonObject do
		var obj = new JsonObject
		if to.is_linked then
			obj["to"] = to.url
		else
			obj["to"] = "\{{to.batch_id.to_s}\}"
		end
		obj["type"] = rel_type
		obj["data"] = properties
		return obj
	end