docs: function do_database_call(Socket, DatabaseType, Request, callback) {
  
  	// Start a new transaction.
  	var transaction_id = 'TX-' + unique_id();
  
  	// Set up the response handler.
  	Socket.once('DocDatabase.' + DatabaseType + '.SubmitQuery.' + transaction_id,
  		function(Err, Response) {
  			if (callback) { callback(Err, Response); }
  			return;
  		});
  
  	// Invoke the function.
  	Request.control = {};
  	Request.control.transaction_id = transaction_id;
  	Socket.emit('DocDatabase.' + DatabaseType + '.SubmitQuery', Request);
  
  	return;
  }