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List:       jaxme-dev
Subject:    [jira] [Created] (NEETHI-15) Problem in policy intersection caused by error in PolicyIntersector.com
From:       Jörn_Schneider_(JIRA) <jira () apache ! org>
Date:       2013-09-27 13:17:02
Message-ID: JIRA.12670934.1380287761460.29920.1380287822460 () arcas
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Jörn Schneider created NEETHI-15:
------------------------------------

             Summary: Problem in policy intersection caused by error in \
PolicyIntersector.compatiblePolicies method  Key: NEETHI-15
                 URL: https://issues.apache.org/jira/browse/NEETHI-15
             Project: Neethi
          Issue Type: Bug
    Affects Versions: 3.0.2
            Reporter: Jörn Schneider


Playing around with policy intersection I recognized an unexpected result of getting \
an empty policy back even though the two intersected policies do have a common \
compatible policy assertion alternative.  As examples I was using the first example \
from chapter 4.5 Policy Intersection \
http://www.w3.org/TR/ws-policy/#Policy_Intersection. 

Using Neethi the intersected policy returned an empty policy as result even though \
Alternative A2 from input Policy P1 and Alternative A3 from input Policy P2 are \
compatible alternatives.

What I did was reading the policies from XML file (policies attached) and just \
intersecting them:

Policy inputPolicy1 = readPolicy("inputPolicy1.xml");
Policy inputPolicy2 = readPolicy("inputPolicy2.xml");
Policy intersectionP1_P2 = inputPolicy1.intersect(inputPolicy2, false);    
 
I also recognized that changing order while intersecting the policies returned the \
expected result: Policy intersectionP2_P1 = inputPolicy2.intersect(inputPolicy1, \
false);

The difference was caused by the result of 'compatiblePolicies' method call used in \
line 189 of method PolicyIntersector.intersect. The call \
compatiblePolicies(inputPolicy1, inputPolicy2) is returning false the reversed call \
compatiblePolicies(inputPolicy2, inputPolicy1) returns true.

In addition I also tried the intersection example from the following web page
http://www.ibm.com/developerworks/webservices/tutorials/ws-understand-web-services5/section5.html


I also attached intersect1.xml and intersect2.xml for convenience.

Here always an empty policy was returned by the intersection call independent of the \
order the incoming policies were used. A closer look to the implementation of method \
'PolicyIntersector.compatiblePolicies' revealed the reason. The return false; \
statement on line 178 in the outer while loop:

    public boolean compatiblePolicies(Policy p1, Policy p2) {       
        Iterator<List<Assertion>> i1 = p1.getAlternatives();
        while (i1.hasNext()) {
            List<Assertion> alt1 = i1.next();
            Iterator<List<Assertion>> i2 = p2.getAlternatives();
            if (!i2.hasNext() && alt1.isEmpty()) {
                return true;
            }
            while (i2.hasNext()) {                
                List<Assertion> alt2 = i2.next();
                if (compatibleAlternatives(alt1, alt2)) {
                    return true;                    
                }
            }             
            return false;
        }        
        return true;
    }
 
The 'return false;' statement inside the outer while loop has the effect that only \
the first alternative of Policy p1 is evaluated against all alternatives from Policy \
p2.  
My correction proposal is to remove the return statement on line 178 and change the \
return statement on line 180 to return false instead of true. With this changes \
'compatiblePolicies' should return true only if compatible alternatives are found in \
p1 and p2 and false otherwise.

    public boolean compatiblePolicies(Policy p1, Policy p2) {       
        Iterator<List<Assertion>> i1 = p1.getAlternatives();
        while (i1.hasNext()) {
            List<Assertion> alt1 = i1.next();
            Iterator<List<Assertion>> i2 = p2.getAlternatives();
            if (!i2.hasNext() && alt1.isEmpty()) {
                return true;
            }
            while (i2.hasNext()) {                
                List<Assertion> alt2 = i2.next();
                if (compatibleAlternatives(alt1, alt2)) {
                    return true;                    
                }
            }             
        }        
        return false;
    }


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