@Override
	public void removeProductType(ProductType productType) {
		tx.begin();
		for (SubProcess sp : productType.getSubProcesses()) {
			for (Stock s : sp.getStocks()) {
				sp.removeStock(s);
			}
			em.merge(sp);
			em.remove(sp);
		}
		em.remove(productType);
		tx.commit();
	}