Jörn Schneider created NEETHI-15:
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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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