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

> policy is used to convey conditions on an interaction between entities

What do you mean by policy ? Is this assertions or alternative or both?

Anthony Nadalin | Work 512.838.0085 | Cell 512.289.4122


                                                                           
             "Sverdlov, Yakov"                                             
             <Yakov.Sverdlov@c                                             
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             request@w3.org                                                
                                                                   Subject 
                                       Re: NEW ISSUE: Clarify the policy   
             09/13/2006 09:26          model for Web Services              
             AM                                                            
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Hi,

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

Regards,

Yakov Sverdlov
CA

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.