It is possible to change the response to any question by posting a new response to an earlier question. However, this may change the routing path and invalidate the URLs to proceeding questions. When this occurs, and a later URL is subsequently used to post an answer, the interview will be advanced to that question using the previously provided answers. If is not possible to retrieve the requested save point, the response will instead be the first question for which no previous answer is available (or for which a response is available but is not valid). This is standard Interview Object Model (IOM) behavior when it receives a POST for a different save point rather than the current save point. No additional handling is required by the Interview Web Service.

The Interview Web Service automaticallys assign new interviews to an engine and the response URL contains the engine name. If the engine fails, the interview is routed to a new engine. This results in the POST returning the next page, but the page is on a different engine.

For this reason, past URLs should never be cached. If the client must navigate to a previous question, the interview should include Goto navigation in the page and the client should specify a Goto save point when it posts the answer.