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Re: ISSUE (3639) Which policy alternative was selected?

From: Sergey Beryozkin <sergey.beryozkin@iona.com>
Date: Tue, 31 Oct 2006 17:42:36 -0000
Message-ID: <024401c6fd13$f3bc07b0$3901020a@sberyoz>
To: "Yalcinalp, Umit" <umit.yalcinalp@sap.com>, "Sanka Samaranyake" <sanka@wso2.com>, "Fabian Ritzmann" <Fabian.Ritzmann@Sun.COM>
Cc: "Ashok Malhotra" <ashok.malhotra@oracle.com>, <public-ws-policy@w3.org>

Hi all,

Can you please clarify a couple of things...
I don't understand why a service provider needs to know which policy alternative was selected.
I feel what Daniel suggested about attaching policies to different endpoints should be an adequate approach for most cases, because
this is what endpoints are for in the first place.
If two alternatives can be meaninfully/usefully created in a scope of a single endpoint then it's fine (security related
alternatives, etc), this is also probably useful when nested polices are used.

I've read the proposal for optional assertions and the suggestion to mark with wsp:optional something a provider will not always do
and to enable optional behaviours out-of-band, perhaps by letting a provider know which policy alternative was selected.
I'm confused. For example :

<custom:MTOM wsp:optional/>

it says custom:foo is something a provider won't always do and it will do only if it's told somehow by a requester to do it.

So here we go :

<Policy>
   <ExactlyOnce>
   <!-- Alt1 -->
   <All>
     <custom:bar/>
   </All>
   <!-- Alt2 -->
   <All>
     <custom:MTOM/>
     <custom:bar/>
   </All>
   </ExactlyOnce>
</Policy>

By selecting the second alternative and by the virtue of sending MTOM-serialized messages the requester is saying to a provider that 
it needs to load its <custom:MTOM/> handler. I don't see a reason for some more out-of-band indication that alternative2 was 
selected.

In what cases one would want to explicitly tell the provider which alternative was selected ?

Thanks, Sergey





I agree. We should definitely acknowledge that this is a problem even if
we may choose not to tackle it in an interoperable way in this version.

Please see that the proposal for optional assertions that I sent a while
back also contains some language for out of band mechanisms in order to
make messages self describing (which includes the option of an
additional protocol).

--umit


> -----Original Message-----
> From: public-ws-policy-request@w3.org
> [mailto:public-ws-policy-request@w3.org] On Behalf Of Sanka
> Samaranyake
> Sent: Tuesday, Oct 10, 2006 12:55 PM
> To: Fabian Ritzmann
> Cc: Ashok Malhotra; public-ws-policy@w3.org
> Subject: Re: ISSUE (3639) Which policy alternative was selected?
>
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Fabian Ritzmann wrote:
> >
> > Ashok Malhotra wrote:
> >> My original motivation in raising this issue was to provide a
> >> rationale for why we
> >> wanted a pointer from the message to the policy (alternative) that
> >> was applied to it.  (There are
> >> other reasons why such a pointer may be useful, for example if the
> >> policy changes
> >> during the course of a long-running transaction, or to indicate
> >> policies or assertions which do not affect the wire format of
> >> messages - bug 3789.)
> >>
> >> At the f2f in Bellevue the WG said:
> >> 1. You can add such a pointer to a msg using the SOAP extensibility
> >> mechanism but
> >> 2. The WG did not want to standardize such a header as it raised
> >> all manner of questions such "shd this
> >> be the first header."
> >>
> >> Subsequently, Dan Roth told the WG
> >>
> http://lists.w3.org/Archives/Public/public-ws-policy/2006Oct/0043.html
> >> that Microsoft products used the following solutions:
> >> 1. In case multiple alternatives apply, create an endpoint that
> >> supports exactly one policy alternative.
> >> 2. Use an out-of-band mechanism to convey which alternative was
> >> selected.  In effect, this uses an out-of-band
> >> mechanism instead of the pointer in the message that I wanted.
> >>
> >> So, at this point I am willing to agree to close the issue with no
> >> action.
> >> If others feel differently please propose the solution you
> would like.
> >>
> >
> > Regarding the suggested solutions:
> >
> > 1. Web services are meant to be interoperable. I don't think that
> > any product-specific solution can satisfy that requirement.
> >
> > 2. Irrespectively of whether an in-band or out-of-band mechanism is
> > chosen, it would be beneficial to have standardized solutions.
> >
> > Having said that, I believe that designing a solution would take
> > more time and effort than would be good for our schedule. I'd like
> > to see this issue deferred to V.next.
> >
> > Fabian
> >
>
> I believe as policies are get used in more and more real life
> scenarios, it is likely that we might end up with policy alternatives
> that are not distinguish able just looking at the message itself. And
> I feel that, irrespectively of whether it is in-band or out-of-band,
> there should be way to indicate to the server, which alternative the
> client has picked. I am ok if with differing this  to the next version
> as far as  it  is remains noted.
>
> Sanka
>
> - --
> Sanka Samaranayake
> WSO2 Inc.
> T:+94-77-3506382 F:+94-11-2424304
>
> http://sankas.blogspot.com/
> http://www.wso2.net/
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Received on Wednesday, 1 November 2006 01:32:30 GMT

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