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Bug 3789 - Clarify usage of assertions with no behavioral requirements on the requester
Summary: Clarify usage of assertions with no behavioral requirements on the requester
Alias: None
Product: WS-Policy
Classification: Unclassified
Component: Framework (show other bugs)
Version: PR
Hardware: PC Windows XP
: P2 normal
Target Milestone: ---
Assignee: Sergey Beryozkin
QA Contact: Web Services Policy WG QA List
Depends on:
Reported: 2006-10-03 21:34 UTC by Sergey Beryozkin
Modified: 2006-11-09 14:30 UTC (History)
1 user (show)

See Also:


Description Sergey Beryozkin 2006-10-03 21:34:49 UTC
Target : WS-Policy Framework and policy guidelines

Justification :

There's a class of policy assertions which have no behavioral requirements on the requester but can be still usefully processed by requesters which are aware
of what assertions mean. 
For example : <oasis:Replicatable/>

An assertion like this one can be a useful source of information for requesters. Providers having expected properties like <oasis:Replicatable/> can be chosen/searched. 
At the same time, given the fact assertions like <oasis:Replicatable/>
have no behavioral requirements on the provider it's important to ensure 
policy-aware clients which have no knowledge of these assertions can proceed
consuming the service advertsing this assertion.

Currently the way to advertise such an assertion is to use a normal form with two policy alternatives(simple case), with only one alternative containing this assertion thus making it optional, or, in other words, giving a chance to requesters to ignore it.
Such normal form expression is equivalent to a compact form with the optional assertion marked with wsp:optional attribute with a value 'true'.

However, at the moment the primer recommends using wsp:optional when one needs to mark asssertions which identify optional capabilities/requirements with behavioral requirements on a requester should the requester wishes to use it. 

Thus marking assertions like <oasis:Replicatable/> with wsp:optional is considered to be a wrong approach.

Proposal : 

Clarify the text describing the optionality in the policy guidelines and in the Framework spec on how a policy author should use assertions like
It's important that assertions like these can be usefully interpreted by knowledgeble requesters and safely ignored by requesters unaware of them.
Comment 1 Sergey Beryozkin 2006-10-06 10:24:19 UTC
This is the resolution I think would adequately address this issue :

1. Add an example to a primer and/or policy guidelines
2. Explain why policy authors should make such assertions optional for those requesters which are not aware of them. 
3. Make any necessary changes to the wsp:optional related wording so that a policy author can use wsp:optional as a recognized but not a workaround way to mark such assertions. 
Comment 2 Paul Cotton 2006-11-09 14:30:11 UTC
Resolved by Treasure Island amended proposal at the Nov F2F in the thread: