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RE: [Bug 4555] Should policy intersection be called policy intersection?

From: Ashok Malhotra <ashok.malhotra@oracle.com>
Date: Thu, 17 May 2007 07:19:37 -0700
To: "David Hull" <dmh@tibco.com>, "Asir Vedamuthu" <asirveda@microsoft.com>
CC: "Paul Cotton" <Paul.Cotton@microsoft.com>, "public-ws-policy@w3.org" <public-ws-policy@w3.org>
Message-ID: <20070517071937797.00000003552@amalhotr-pc>
Let us assume that duplicate alternatives have been removed from the normal form of both policies.

Now, we have 2 sets of alternatives.  If we intersect these 2 sets we get as the result the alternatives that are common to both sets.  Isn't this what we want?  So, I think intersection, explained as above is the correct term.

All the best, Ashok 

________________________________

From: public-ws-policy-request@w3.org [mailto:public-ws-policy-request@w3.org] On Behalf Of David Hull
Sent: Wednesday, May 16, 2007 8:31 PM
To: Asir Vedamuthu
Cc: Paul Cotton; public-ws-policy@w3.org
Subject: Re: [Bug 4555] Should policy intersection be called policy intersection?

 

Asir Vedamuthu wrote: 

	In short, it seems misleading to call "pairwise combination (see 4553)
	of compatible alternatives" "intersection", even though it does in
	some cases act like intersection.
	    

 
It is tempting to think of policy intersection as a set intersection but it is not (for all the reasons that you outlined below). This is why it is called as "Policy Intersection".
  

In my experience in trying to understand Policy Intersection, the fact that it was called "intersection" was a hindrance, not a help, in understanding what was going on.  It's not peanut butter either.  Calling it "Policy Peanut Butter"would distinguish it from "peanut butter" but would not aid in understanding (though it might still be an improvement).

I would have found, say, "Policy Collation" more neutral and thus less misleading.



 
Regards,
 
Asir S Vedamuthu
Microsoft Corporation
 
 
-----Original Message-----
From: public-ws-policy-request@w3.org [mailto:public-ws-policy-request@w3.org] On Behalf Of Paul Cotton
Sent: Sunday, May 13, 2007 12:20 PM
To: public-ws-policy@w3.org
Cc: dmh@tibco.com
Subject: [Bug 4555] Should policy intersection be called policy intersection?
 
 
-----Original Message-----
From: public-ws-policy-qa-request@w3.org [mailto:public-ws-policy-qa-request@w3.org] On Behalf Of bugzilla@wiggum.w3.org
Sent: May 11, 2007 12:02 PM
To: public-ws-policy-qa@w3.org
Subject: [Bug 4555] Should policy intersection be called policy intersection?
 
 
http://www.w3.org/Bugs/Public/show_bug.cgi?id=4555
 
           Summary: Should policy intersection be called policy
                    intersection?
           Product: WS-Policy
           Version: CR
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Framework
        AssignedTo: fsasaki@w3.org
        ReportedBy: dmh@tibco.com
         QAContact: public-ws-policy-qa@w3.org
 
 
The use of "intersection" to describe the operation approximated in section 4.5
is problematic.
 
Intersection usually refers to set intersection of some sort (it might also
refer to bag intersection, given that at least some collections in WS-P are
bags).  Assuming that policies are sets (see 4552), there is some resemblance
between set intersection and policy intersection, in that if it so happens that
alternatives are compatible only when they're identical, the intersection of
two policies will contain one item for each of the alternatives in the set
intersection of the two policies.  If intersection of alternatives turns out to
mean bag intersection (see 4553), then in this particular case policy
intersection will be the set intersection of the two policies.
 
However, if these exact conditions don't hold, then the result is not at all
the set intersection of the two polices.  In particular, two alternatives with
the same assertions but different multiplicities will be compatible, and
alternatives may be compatible even if their component assertions are not
identical, if the assertions are of the same type (or are ignorable in the case
of lax intersection).  In such cases the result may have more alternatives than
either of the policies being intersected, which is counter-intuitive to say the
least.
 
In short, it seems misleading to call "pairwise combination (see 4553) of
compatible alternatives" "intersection", even though it does in some cases act
like intersection.
 
 
  

 
Received on Thursday, 17 May 2007 14:20:32 UTC

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