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Re: SOAP fault required for application error?

From: John Kemp <john.kemp@nokia.com>
Date: Mon, 03 Nov 2008 10:59:41 -0500
Message-ID: <490F1FED.8070303@nokia.com>
To: "ext jim@alanweberassociates.com" <jim@alanweberassociates.com>
CC: xml-dist-app@w3.org

Hello Jim,

ext jim@alanweberassociates.com wrote:
> In a request-response scenario, does SOAP 1.2 require that a SOAP fault be
> returned in the case of an application error?

You have touched on what was a controversial point in development of the 
SOAP specification. Some would say yes, and others probably no.

> In the non-normative SOAP 1.2
> Part 0 document, I find text that says:
> “The SOAP fault model (see SOAP Part 1, section 2.6) requires that all
> SOAP-specific and application-specific faults be reported using a single
> distinguished element, env:Fault, carried within the env:Body element.”
> Which indicates that I am required to return a SOAP fault, but the only
> text I could find in the normative SOAP 1.2 Part 1 document pertaining to
> this says:
> “An ultimate SOAP receiver MUST process the SOAP body, in a manner
> consistent with 2.5 Structure and Interpretation of SOAP Bodies. Failure is
> indicated by the generation of a fault (see 5.4 SOAP Fault). SOAP message
> processing MAY result in the generation of a SOAP fault; more than one 
> SOAP fault MUST NOT be generated when processing a SOAP message.”
> I don't see the word MUST in the sentence "Failure is indicated by the
> generation of a fault" and I do see the word MAY in the phrase "SOAP
> message processing MAY result in the generation of a SOAP fault", so it
> appears to me that I'm not required to return a SOAP fault in the case of
> an application error.

In general, it depends on what you call an application error, and how 
that relates to what you might call an exception.

I believe (and I did spend quite a lot of time working on SOAP) that the 
intent of the SOAP specification is that a SOAP fault is used to 
indicate an exception to normal processing, which is considered a 
separate thing from an application error, occurring during normal 

So if you are a Java programmer, a SOAP fault might be considered 
roughly equivalent to a Java exception - something try-able and 
catch-able. That would be something more significant than an application 
error such as "validation failed for the phone number field".

> Am I interpreting this correctly?

I think so, yes. But I should note that this is my *opinion*, and that 
there may be others on this list who have different ones.

In the end, however, the answer that will make sense for you should 
largely depend on pragmatic concerns - what do your tools/SDKs support? 
Who will you inter-operate with, and what do they expect?


- johnk

> Jim Hollister
Received on Monday, 3 November 2008 16:01:12 UTC

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