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Re: NEW ISSUE: Clarify the policy model for Web Services

From: Sverdlov, Yakov <Yakov.Sverdlov@ca.com>
Date: Wed, 13 Sep 2006 10:26:31 -0400
Message-ID: <ACE36C31EA815A4CBA7EBECA186C0D41BFA875@USILMS13.ca.com>
To: <public-ws-policy@w3.org>


Here's the draft proposal for section 3.4. As you can see, I tried to
minimize the changes.




Yakov Sverdlov



3.4 Policies of Entities in a Web Services-based System

Applied in the Web services-based system, policy is used to convey
conditions on an interaction between entities (requester application,
provider service, Web infrastructure component, etc). Any entity in a
Web services-based system may expose a policy to convey conditions under
which it functions. Satisfying assertions in the policy usually results
in behavior that reflects these conditions. For example, if two entities
- requester and provider - expose their policies, a requester might use
the policy of the provider to decide whether or not to use the service.
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.

A policy assertion is supported by an entity in the web services-based
system if and only if the entity satisfies the requirement (or
accommodates the capability) corresponding to the assertion. A policy
alternative is supported by an entity if and only if the entity supports
all the assertions in the alternative. And, a policy is supported by an
entity if and only if the entity supports at least one of the
alternatives in the policy. Note that although policy alternatives are
meant to be mutually exclusive, it cannot be decided in general whether
or not more than one alternative can be supported at the same time.

Note that an entity may be able to support a policy even if the entity
does not understand the type of each assertion in the vocabulary of the
policy; the entity only has to understand the type of each assertion in
the vocabulary of a policy alternative the entity supports. This
characteristic is crucial to versioning and incremental deployment of
new assertions because this allows a provider's policy to include new
assertions in new alternatives while allowing entities to continue to
use old alternatives in a backward-compatible manner.

Received on Wednesday, 13 September 2006 14:26:36 UTC

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