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RE: NEW ISSUE: "Policy Alternatives" and "Policy" need proper def inition

From: Prasad Yendluri <prasad.yendluri@webmethods.com>
Date: Tue, 1 Aug 2006 20:35:30 -0400
Message-ID: <A3E375FA108EF94496269A5A96AFCAC106504572@mailwest-e0b>
To: Asir Vedamuthu <asirveda@microsoft.com>, Prasad Yendluri <prasad.yendluri@webmethods.com>, Daniel Roth <daniel.roth@microsoft.com>, public-ws-policy@w3.org
Hi Asir,

 

> I noticed that your example policies do not use any nested policy
expression.

 

Section 4.3.3 defines:

 

Equivalence 

wsp:Policy is equivalent to wsp:All 

 

So, for readability, I have not explicitly put wsp:policy brackets around
things and used wsp:All.

 

If my  examples have been, 

 

 Example Policy 1:

 

 <wsp:All> 

   <!-- assertion 5 --> 

   <wsp:ExactlyOne>     

          <!-- assertion 6 --> 

          <!-- assertion 7 -->

   </wsp:ExactlyOne>

  </wsp:All>

 

Example Policy 2:

 

<wsp:All>

  <wsp:ExactlyOne>  

    <!-- assertion 1 -->

    <!-- assertion 2 -->

  </wsp:ExactlyOne>

  <wsp:ExactlyOne>  

    <!-- assertion 4 -->

     . . . .

     <wsp:policy> 

        <!-- assertion 5 -->  

        <wsp:ExactlyOne>   

          <!-- assertion 6 --> 

          <!-- assertion 7 -->

       </wsp:ExactlyOne>

    </wsp:policy>

    . .  .  .

  </wsp:ExactlyOne>

</wsp:All>

 

Would you not then have the same policy alternates for Policy 1 and the
nested policy in policy 2?

I understand the way you came up with the production of the alternatives for
each policy and agree that is the correct way to arrive at them.  The point
of the issue however is that, the text of the specification is not explicit
enough for this. What makes a nested alternative in a Policy specification
not an alternative of the parent policy, when policy is only defined to be
“a collection of policy alternatives”? The nested policy and hence the
embedded alternative is part of the same “collection” is it not?

 

Regards,

Prasad

 

-----Original Message-----
From: public-ws-policy-request@w3.org
[mailto:public-ws-policy-request@w3.org] On Behalf Of Asir Vedamuthu
Sent: Tuesday, August 01, 2006 5:05 PM
To: Prasad Yendluri; Daniel Roth; public-ws-policy@w3.org
Subject: RE: NEW ISSUE: "Policy Alternatives" and "Policy" need proper def
inition

 

Hi Prasad,

 

Thank you for writing down these examples. Let us look at the two policy
expressions in your e-mail below.

 

Policy 1 has two alternatives:

A1 = {assertion 6, assertion 8}

A2 = {assertion 7, assertion 8} 

 

Policy 2 has six alternatives:

A3 = {assertion 1, assertion 4}

A4 = {assertion 2, assertion 4}

A5 = {assertion 1, assertion 5, assertion 6}

A6 = {assertion 1, assertion 5, assertion 7}

A7 = {assertion 2, assertion 5, assertion 6}

A8 = {assertion 2, assertion 5, assertion 7}

 

Two policy alternatives are compatible if each policy assertion in one
alternative is compatible with a policy assertion in the other and
vice-versa. None of the above policy alternatives are compatible. 

 

Two policies are compatible if a policy alternative in one is compatible
with a policy alternative in the other. Policy 1 and Policy 2 are
incompatible because none of the policy alternatives in Policy 1 is
compatible with a policy alternative in Policy 2.

 

Just as expected, these two policies are incompatible. I noticed that your
example policies do not use any nested policy expression.

 

I hope this helps.

 

PS: I’ll update your entry in Bugzilla.

 

Regards,

 

Asir S Vedamuthu

Microsoft Corporation

 

________________________________________

From: public-ws-policy-request@w3.org
[mailto:public-ws-policy-request@w3.org] On Behalf Of Prasad Yendluri

Sent: Monday, July 31, 2006 5:32 PM

To: Daniel Roth; Prasad Yendluri; public-ws-policy@w3.org

Subject: RE: NEW ISSUE: "Policy Alternatives" and "Policy" need proper def
inition

 

Dan,

 

Policy is defined to be a “collection of policy alternatives” only. Since
an assertion in policy alternative can embed another policy (as defined
below), a policy can end-up with policy alternatives in the policy embedded
(in an assertion of an alternative).

 

   <Assertion …>

  …

  ( <wsp:Policy …> … </wsp:Policy> )?

  …

</Assertion>

 

There is generally no ambiguity until we run into further specifications
that state things like “Two policies are compatible if an alternative in
one is compatible with an alternative in the other.”

 

Suppose you have the following two Policy specifications:

 

            Example Policy 1:

 

 <wsp:All> 

   <wsp:ExactlyOne>      <!-Alternative A →

          <!-- assertion 6 --> 

          <!-- assertion 7 -->

   </wsp:ExactlyOne>

   <!-- assertion 8 -->  <!-Alternative B →

</wsp:All>

 

               Example Policy 2:

 

<wsp:All>

  <wsp:ExactlyOne>  <!-Alternative 1 Top level →

    <!-- assertion 1 -->

    <!-- assertion 2 -->

  </wsp:ExactlyOne>

  <wsp:ExactlyOne>  <!-Alternative 2 Top level →

    <!-- assertion 4 -->

    <wsp:All> 

        <!-- assertion 5 -->  <!-Alternative 3 Nested →

        <wsp:ExactlyOne>      <!-Alternative 4 Nested →

          <!-- assertion 6 --> 

          <!-- assertion 7 -->

       </wsp:ExactlyOne>

    </wsp:All>

  </wsp:ExactlyOne>

</wsp:All>

 

 

Turns out <!-Alternative A → in Example Policy 1 is compatible with (same
definition as) the “nested” policy alternative marked 

<!-Alternative 4 Nested → in Example Policy 2.

 

Then using the definition, “Two policies are compatible if an alternative
in one is compatible with an alternative in the other.”, one can conclude
that Example Policy 1 and Example Policy 2 are compatible, without further
qualification of “alternative in a policy”. In reality, the policies are
not compatible of course even though, based purely on the current definition
of policy (and other related entities), one can arrive at that conclusion.

 

Hope that clarifies the issue.

 

Regards,

Prasad

 

________________________________________

From: public-ws-policy-request@w3.org
[mailto:public-ws-policy-request@w3.org] On Behalf Of Daniel Roth

Sent: Monday, July 31, 2006 4:24 PM

To: Prasad Yendluri; public-ws-policy@w3.org

Subject: RE: NEW ISSUE: "Policy Alternatives" and "Policy" need proper
definit ion

 

I’m having difficulty understanding this issue.  Some examples that
demonstrate how the current definitions are ambiguous would be helpful.

 

Thanks.

 

Daniel Roth

 

________________________________________

From: public-ws-policy-request@w3.org
[mailto:public-ws-policy-request@w3.org] On Behalf Of Prasad Yendluri

Sent: Wednesday, July 26, 2006 4:15 PM

To: public-ws-policy@w3.org

Subject: NEW ISSUE: "Policy Alternatives" and "Policy" need proper definit
ion

 

Title: "Policy Alternatives" and "Policy" need proper definition

 

Description: Section 2.3 terminology defines a “policy” to be, “a
collection of policy alternatives”

No further constraints on how these alternatives are grouped, i.e. on the
origin of alternatives in the collection.

 

Similarly section 3.2 (Policy) defines a “policy” to be: “a policy is a
potentially empty collection of policy alternatives.”

 

This “collection” does not account for level of nesting of a specific
policy alternative. 

 

Section 2.3 terminology defines a “Policy Alternative” to be “a
collection of policy assertions” only. 

No further restriction on how these assertions are grouped (or) the origin
of the assertions in the collection.

 

 

Similarly section 3.2 (Policy Alternative) defines a policy alternative to
be: 

“A policy alternative is a logical construct which represents a potentially
empty collection of policy assertions. An alternative with zero assertions
indicates no behaviors.”

 

This “collection” again does not account for level of nesting of a policy
assertion included.

 

Justification:

There is scope for interpretation that needs to be eliminated. “policy
assertion” and “policy” definitions need to account for level of nesting
of the collection they define. 

 

Target: WS-Policy 1.5 - Framework

 

Proposal - Tighten up the definitions of “policy” and “policy
assertion”. Sorry I have not come up suggestion for a specific replacement
text at this point.

Hope to follow-up later.

 

 

Regards,

Prasad Yendluri

 
Received on Wednesday, 2 August 2006 00:36:50 GMT

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