Thanks Mike, I have found and solved the problem, I'll commit the fix together with some other improvements in the next few days. Can you open a JIRA for this? The problem here is that, in order to be "traited", objects need a few additional internal structures, hence the reason for the @Traitable annotation. With declared beans, these structures are added automatically to the class generated on the fly. With "legacy" (pojo) beans, that is impossible - by convention we are not touching legacy classes - so a wrapper is generated internally instead. When you applied the "isA" operator to a legacy object type, the operator was looking for those additional structures. I have modified the operator to go and look for the wrapper corresponding to an object, so calling isA on a legacy bean WILL be possible, but discouraged. Another option would be : when  $p : PojoFact( ... )  [ not / exists ] Thing( core == $p ) then All traits implement Thing, so this rule effectively looks for legacy objects which have (not) been traited. You can use more specific types than "Thing" if you want. With respect to "isA", which probably will be renamed "hasType", this will also be triggered by more specific traits. Remember that traits are interfaces, so inheritance is possible. The drawback here is that your legacy bean must implement equals() ad hashCode() appropriately, considering that an object might be compared not just with itself or objects of the same class, but also with instances of proxy subclasses. For example, in your case you should write something like:    @Override    public boolean equals(Object o) {        if (this == o) return true;        if ( ! ( o instanceof PojoFact ) ) return false;        PojoFact pojoFact = (PojoFact) o;        if ( getId() != pojoFact.getId() ) return false;        return true;    }    @Override    public int hashCode() {        return id;    } Feel free to ask more questions and report more bugs and suggestions ;) The code is very experimental and still work in progress, in time it will come with better robustness and documentation Best Davide -- View this message in context: http://drools.46999.n3.nabble.com/rules-users-Possible-bug-with-isA-opera... Sent from the Drools: User forum mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users