A REST response is an easy to understand XML block.

Response

<?xml version="1.0" encoding="utf-8" ?>
<rsp status="ok">
   -xml-data-
</rsp>

Error Response

<?xml version="1.0" encoding="utf-8" ?>
<rsp status="error">
   <error code="150" msg="An error occurred with error code 150" />
</rsp>