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Re: Behaviour of WS-Policy aware clients

From: Maryann Hondo <mhondo@us.ibm.com>
Date: Tue, 19 Sep 2006 15:34:07 -0400
To: "Sergey Beryozkin" <sergey.beryozkin@iona.com>
Cc: public-ws-policy@w3.org, public-ws-policy-request@w3.org, "Sergey Beryozkin" <sergey.beryozkin@iona.com>
Message-ID: <OF62BDDA20.DE17C66B-ON872571EE.006964AD-852571EE.006B4FFF@us.ibm.com>
Sergey,
We're currently working on clarifying the text.
In the interim, I'll give you my opinion.

First of all, the goal of policy is to have assertions define the 
capabilities and constraints of an "entity" ( we are working on changing 
"requestor" and "provider" to "entity" with an e.g, requestor/provider) to 
enable interoperability of web services.

So, if a "provider" indicates a constraint ( let's assume its " all 
messages to me must be signed") and you don't know what that means, then 
chances are any attempt to send a message to the provider will fail.  If 
you're really, really lucky, and you always sign all your messages maybe 
you'll guess right on the algorithm and other metadata about signing, but 
its kind of a long shot.

For 2, again, the idea here is if you are the "provider of a service" you 
probably want people to get messages to you (othewise, why expose a 
service?).
If you support a whole bunch of options, but don't tell anyone about it, 
chances are a few people may try, but if they try and fail, not many 
people are going to keep trying to send you messages with every possible 
alternative configuration.
Maybe you have something that people can't live without and they're 
willing to try, try again, but I find there's a point at which they will 
move on to someone who is clear about their expectations thus increasing 
their chance of success.The intent of web services is to enable 
interoperability, if you want to hide why bother exposing your services?

In order to demonstrate interoperability there are some requirements:

A requester may choose any alternative since each is a valid configuration 
for interaction with the service, but a requester MUST choose only a 
single alternative for an interaction with a service since each represents 
an alternative configuration.

If an assertion in the normal form of a policy expression contains a 
nested policy expression, the nested policy expression MUST contain at 
most one policy alternative 

but there is not currently normative text that I'm aware of that says "A 
client MUST not send a message" because I'm not sure how anyone would 
enforce this.

Maryann





"Sergey Beryozkin" <sergey.beryozkin@iona.com> 
Sent by: public-ws-policy-request@w3.org
09/19/2006 12:29 PM

To
"Sergey Beryozkin" <sergey.beryozkin@iona.com>, <public-ws-policy@w3.org>
cc

Subject
Behaviour of WS-Policy aware clients






Hello
 
A couple of questions on the expected behaviour of a WS-Policy aware 
client.
 
1. Suppose we have a policy with a *single* alternative which a 
policy-aware client can not support
due to the fact it does not *recognize* its assertions (no intersection is 
involved).
Is it expected to fail ? Can it attempt to initiate a communication with 
the provider ?
 
1. Suppose we have a policy which a policy-aware client can not support
due to the fact an intersection produced an empty set.
Is it expected to fail ? Can it attempt to initiate a communication with 
the provider ?
 
Thanks, Sergey Beryozkin
Iona Technologies
Received on Tuesday, 19 September 2006 19:32:22 GMT

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