protected boolean isConflictRules(Rule r1, Rule r2) throws TheoryNormalizerException {
		logMessage(Level.FINER, 1, "verify conflict rules", r1.getLabel(), r2.getLabel());
		boolean isConflictRule = false;
		List<Literal> r1Heads = r1.getHeadLiterals();
		List<Literal> r2Heads = r2.getHeadLiterals();
		for (int j = 0; !isConflictRule && j < r1Heads.size(); j++) {
			Literal r1Head = r1Heads.get(j);
			Set<Literal> conflictLiterals = getConflictLiterals(r1Head);
			for (int i = 0; !isConflictRule && i < r2Heads.size(); i++) {
				Literal r2Head = r2Heads.get(i);
				if (conflictLiterals.contains(r2Head)) isConflictRule = true;
				logMessage(Level.FINEST, 2, "verify conflict literals", r1Head, r2Head, "isConflictRule=" + isConflictRule);
			}
		}
		return isConflictRule;
	}