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RE: [Requirements] Non-requirement for MEPs

From: Assaf Arkin <arkin@intalio.com>
Date: Wed, 19 Mar 2003 11:57:46 -0800
To: "Patil, Sanjaykumar" <sanjay.patil@iona.com>
Cc: <public-ws-chor@w3.org>

> -----Original Message-----
> From: public-ws-chor-request@w3.org
> [mailto:public-ws-chor-request@w3.org]On Behalf Of Patil, Sanjaykumar
> Sent: Wednesday, March 19, 2003 10:20 AM
> To: Assaf Arkin
> Cc: public-ws-chor@w3.org
> Subject: RE: [Requirements] Non-requirement for MEPs
> >> <Assaf>
> >> I'm not sure there is much value in identifying specific
> faults, I think
> >> some coarse distinction will suffice.
> >> For example, the seller may send a message that the buyer
> cannot validate.
> >> The buyer can send back some fault. But the seller may
> validate the message
> >> on its side before sending it, determine the fault without
> having to receive
> >> it from the buyer. The seller may find that it's
> implementation is wrong and
> >> it cannot proceed. It's able to fix the implementation but
> that may take
> >> longer than the transaction timeout. So suffice that the seller can say
> >> 'oops, something went wrong, let's decide to cancel the transaction'. I
> >> don't think there's need to delve into the what went wrong in
> much detail,
> >> coarse grain would work fine for all the scenarios I've seen.
> >> </Asaaf>
> Even to say that "oops, something went wrong, let's decide to
> cancel the transaction", you need to know the exact type of the
> error. That is, if you wanted to define the behavior of the
> system to cancel the transaction for certain types of errors, you
> are already assuming that you can identify the types of errors.
> Isn't specifying the type of the error already getting into
> defining details of the error message!

But I can do that in a very generic way.

It's possible that a message has a well formed error, validation error,
attachment corrupt error, mandatory header not supported error, or
decryption failure error. At the choreography level do I care which of these
errors prevented the message from being processed? Or can I just forumlate
the behavior in terms of a very generic error (like error = SOAP server
fault) ignoring the details?

This is different from business errors, which may have more specific effect
on the flow, errors like:

- The product is not available, please update your catalog
- The quoted price is no longer accepted, please obtain a new quote
- Cannot possibly ship by this date, alternative date provided

You would want to clearly define these errors and use suitable messages.
Usually these are messages, not specifically faults (in the WSDL term). Even
if you decide to use faults, you can still define these faults precisely
using WSDL and address them specifically using a fault handler.

The issue here - as I understood from reading Edwin's e-mail - is that the
faults listed above (invalid, unsupported header, etc) are not well defined.
For the implementation this is an issue, but for the choreography I have yet
to see a use case that distinguishes between failure due to invalid vs
failure due to malformed. I do see a difference between these generic
"server faults" and other type of errors, but the other type of errors can
be well defined by creating specific message definitions for them.


> Once we support certain types of errors,  we may also have to
> augment the error message definitions with the exact information
> of the error instance. For example, a content-validation-failed
> error message can include the details of which element in which
> document was the culprit.
> Yes, a coarse grained error type is useful in its own merit and
> we could include such a category to account for unidentified
> errors. However, for those functionalities that will be directly
> supported by the choreography specification, we need to clearly
> support the relevant error messages also.
> Sanjay Patil
> Distinguished Engineer
> sanjay.patil@iona.com
> -------------------------------------------------------
> IONA Technologies
> 2350 Mission College Blvd. Suite 650
> Santa Clara, CA 95054
> Tel: (408) 350 9619
> Fax: (408) 350 9501
> -------------------------------------------------------
> Making Software Work Together TM
Received on Wednesday, 19 March 2003 14:58:52 UTC

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