Requirements for a PhD
The formal requirements for a PhD can be found in the PhD regulations.
The content related aspiration level is based on the performances that are expected by research assistants. It is expected, that scientific publications are written and published preferably in international journals.
The expectations are lower for an external PhD, which may be expressed by a corresponding grading, but one has to note that an external PhD will only be successful, if enough time is reserved for the work on the dissertation. PhDs which are realized exclusively as a side job, have failed so far.