[jboss-jira] [JBoss JIRA] (DROOLS-1543) DMN ItemDefinition dependencies ordering

[Matteo Mortari (JIRA)]

Matteo Mortari created DROOLS-1543:
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             Summary: DMN ItemDefinition dependencies ordering
                 Key: DROOLS-1543
                 URL: https://issues.jboss.org/browse/DROOLS-1543
             Project: Drools
          Issue Type: Bug
            Reporter: Matteo Mortari
            Assignee: Matteo Mortari


Using Java-api Comparator is not easily suitable to address the problem of ordering the ItemDefinition by their dependencies.

If the Comparator is used to check purely for dependencies, returning 0 for indipendent elements, assume the following:

{code:java}
X
Y -> Z
{code}

where X is independent from Y, Z; and Y depends on Z.

{code:java}
compare(X, Y) == 0 // by definition above

compare(X, Z) == 0 // still, by definition above, X is independent also from Z
compare(Y, Z) == 1 // because Y depends on Z, Y is bigger than Z.
{code}

The above breaks the API contract in the Java-API Comparator where stating:
{quote}Finally, the implementor must ensure that compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z.{quote}



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