Re: Issue 168 (Which Operation?) / Requirement R114

Hi David.

* David Booth <dbooth@w3.org> [2004-06-30 14:18-0400]
> This message contains a fairly detailed analysis of issue 168 / requirement 
> R114.
[..]
> R114
>     The description language MUST allow unambiguously mapping any
> on-the-wire Message to an Operation. (From WG discussion. Last revised 4
> Apr 2002.)
[..]

Thank you for this excellent analysis. I think that you framed the
problem very well.

> OPTIONS FOR MOVING FORWARD
> I believe the scenario above illustrates the heart of this dilemma.  Would 
> this scenario represent an acceptable reality?  Or should this WG try to 
> prevent it?  If so, how?
> 
> We are now approaching Last Call, which is the time when we announce to the 
> world that we believe we have met all of our requirements.  We cannot 
> afford to delay LC, but we obviously have not yet met requirement 
> R114.  What should we do?  I see a few options.
> 
> Option 1a: Rescind requirement R114.
> 
> Option 1b: Acknowledge in our LC draft that R114 has not been met, without 
> formally rescinding it.  At this point I don't know if there is much 
> difference between this option and option 1a.  Either one is likely to 
> result in minority opinions being filed.
> 
> Option 2: Come up with a new proposal and adopt it.  (But we are running 
> out of time to do so.)
> 
> Option 3: Reconsider an existing proposal.

I have been thinking about this over the past few days, and I reached
the following conclusions.
- this is an interoperability problem: as scenario X shows, it means
  that a WSDL document could potentially not describe a service
  precisely enough to allow the use of it.
- there are ways to address the problem, that do not constrain
  described services: while the unique GED proposal constrains
  services, the WS-Addressing/WS-MD/operation name feature proposals
  allow to disambiguate such cases.
- because of its extensibility, WSDL 2.0 allows one to specify that
  the use of such a mechanism is required in order to use the service
  properly and unambiguously.

Therefore, thinking out loud, I think that we could say in Part 1
that, if the GED of operations is not unique, extra information must
be used in order to unambiguously identify the operation relating to a
message received by a service, by using a feature at the interface
operation level. We could even define such a feature, say the
Operation Name Specification Feature, which would be an abstract
feature: we would not define how it is implemented (in SOAP, HTTP, or
any other way), just noting that its use makes the receiver of the
message aware of which operation the message is related to.

WS-Addressing, WS-MD, Glen/Umit Operation Name, etc.  could then claim
that they implement the Operation Name Specification Feature and
therefore are valid solutions to this problem.

And I believe that R114 would be met since WSDL 2.0 would allow such a
description.

Comments?

Regards,

Hugo

-- 
Hugo Haas - W3C
mailto:hugo@w3.org - http://www.w3.org/People/Hugo/