[cgiapp] Best practice for CGI errors

[Mark Knoop]

Hi

I suspect the reason I can't fun the answer for this is that it is too 
obvious... but I am having a moment of doubt!

If one wants to return an error to the client because they have not included 
the correct parameters for the CGI request, should one use one of the HTTP 
status codes and if so which one? And then is it ok/sensible to include an 
error message in the body?

Or should success or failure at the app level be indicated solely in the 
body of the response, with the HTTP response codes only being used to 
indicate an HTTP error ie if they don't include the correct parameters for 
one's app but it is still a valid HTTP request then use 200 but have some 
error notification inside the response body. If this is the case is there 
any kind of standard practice?

I should probably mention that I am not responding with HTML here but rather 
this is a simple API or 'web service' - however I was hoping to avoid using 
SOAP or the like as it is very simple and CGI style GET with the return 
value in the response body should work fine - just having a momentary 
quandary on the error issue.

Any suggestions gratefully receieved!

Cheers
Mark