Sometimes you will get into trouble if you need to have different package names based on yours project version number? You think this nonsense? Ok…Let’s give an example. If you are generating JAXB classes from appropriate XSD’s and you have different XSD versions which you have to make available? Ok. You will say simply make different versions etc. but the real problem arise if you need different XSD’s versions within the same project? This is the time where you need such a thing.