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

From: Prasad Yendluri <prasad.yendluri@webmethods.com>
Date: Wed, 2 Aug 2006 23:18:28 -0400
Message-ID: <A3E375FA108EF94496269A5A96AFCAC106504ED2@mailwest-e0b>
To: Anthony Nadalin <drsecure@us.ibm.com>, Asir Vedamuthu <asirveda@microsoft.com>
Cc: Asir Vedamuthu <asirveda@microsoft.com>, Daniel Roth <daniel.roth@microsoft.com>, Prasad Yendluri <prasad.yendluri@webmethods.com>, public-ws-policy@w3.org, public-ws-policy-request@w3.org
Hi Asir,

 

Yes the example below does have a nested policy.  I used … around the <wsp:
policy> elements  on purpose, to skip some unnecessary detail, that are not
needed to illustrate the issue at hand.

 

The point is that the nested policy in  “Example Policy 2” has policy
alternatives that are identical to the policy alternatives in “Example
Policy 1”.

With the current (somewhat loose) specification of a policy to be a
collection of policy alternatives, one can deduce that the alternatives in
the nested Policy specification are alternatives of the parent policy also,
which match the alternatives in “Example Policy 1” (and hence the two
policies are compatible etc.).  

 

It would be helpful to have more concrete definitions.

 

Regards,

Prasad

 

  _____  

From: Anthony Nadalin [mailto:drsecure@us.ibm.com] 
Sent: Wednesday, August 02, 2006 6:56 PM
To: Asir Vedamuthu
Cc: Asir Vedamuthu; Daniel Roth; Prasad Yendluri; public-ws-policy@w3.org;
public-ws-policy-request@w3.org
Subject: RE: NEW ISSUE: "Policy Alternatives" and "Policy" need proper def
inition

 

The example below does have nesting, as there is TransportBinding assertion
that has an AlgorithmSuite assertion and so on and so on

Anthony Nadalin | Work 512.838.0085 | Cell 512.289.4122
Inactive hide details for "Asir Vedamuthu" <asirveda@microsoft.com>"Asir
Vedamuthu" <asirveda@microsoft.com>




"Asir Vedamuthu" <asirveda@microsoft.com> 
Sent by: public-ws-policy-request@w3.org 

08/02/2006 04:09 PM




To


"Asir Vedamuthu" <asirveda@microsoft.com>, "Prasad Yendluri"
<prasad.yendluri@webmethods.com>, "Daniel Roth" <daniel.roth@microsoft.com>,
<public-ws-policy@w3.org>




cc






Subject


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

 







In the example below, it is not clear to me where assertions start and end.
As described in Section 4.3.2 [1], a nested policy expression is a policy
expression that is a child element of a policy assertion element:

"Any policy assertion MAY contain a nested policy expression. The schema
outline for a nested policy expression is:

<Assertion …>
 …
 ( <wsp:Policy …> … </wsp:Policy> )?
 …
</Assertion>"

In the example below, it does not look like any of these assertions have
nested policy expressions. Was this intentional? The normative text in
Section 4.3.2 seems to be clear that this must be the case.

[1]
http://www.w3.org/TR/2006/WD-ws-policy-20060731/#Policy_Assertion_Nesting
<http://www.w3.org/TR/2006/WD-ws-policy-20060731/#Policy_Assertion_Nesting> 

Regards,
 
Asir S Vedamuthu
Microsoft Corporation

________________________________________
From: public-ws-policy-request@w3.org
[mailto:public-ws-policy-request@w3.org <mailto:public-ws-policy-request@w3.
org> ] On Behalf Of Asir Vedamuthu
Sent: Wednesday, August 02, 2006 7:12 AM
To: Prasad Yendluri; Daniel Roth; public-ws-policy@w3.org
Subject: RE: NEW ISSUE: "Policy Alternatives" and "Policy" need proper def
inition

RE the text of the specification is not explicit enough for this

A full worked out example that demonstrates how the current definitions are
ambiguous or not explicit enough is the best way to move forward on this.

Regards,
 
Asir S Vedamuthu
Microsoft Corporation

________________________________________
From: Prasad Yendluri [mailto:prasad.yendluri@webmethods.com <mailto:prasad.
yendluri@webmethods.com> ] 
Sent: Tuesday, August 01, 2006 5:36 PM
To: Asir Vedamuthu; Prasad Yendluri; Daniel Roth; public-ws-policy@w3.org
Subject: RE: NEW ISSUE: "Policy Alternatives" and "Policy" need proper def
inition

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 <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 <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 <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 <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




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Received on Thursday, 3 August 2006 03:19:51 UTC

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