Selected components of a piece of software serve in a first variant, as variation points, are converted into a first XML code. The software, now in hybrid form, is shipped. The first code is converted on the customer side via one or more transformations, for example SLT, exclusively in accordance with transformation rules into a second XML code. In a second variant, a first XML code containing at least one language extension is converted in accordance with transformation rules into a more easily verifiable second XML code without said language extensions. In a third variant a source code formulated in XML is transformed in such a way that, following a back-conversion into the original programming language, a new source code is produced in which not only the representation, but also the actual program content and/or functionality has been changed. Alternatively, in a fourth variant a source code formulated in XML with, for example, initial states, code fragments to be replaced and foreign language modules tailored to the respective natural language of the user is mixed by transformation, as a result of which, following a back-conversion, a new source code is produced in which not only the representation, but also the actual program content and/or functionality has been changed.