public function setOutcomeRules(OutcomeRuleCollection $outcomeRules)
    {
        if (count($outcomeRules) > 0) {
            $this->outcomeRules = $outcomeRules;
        } else {
            $msg = "An OutcomeIf object must be bound to at least one OutcomeRule.";
            throw new InvalidArgumentException($msg);
        }
    }