If an applicant meets all requirements for acceptance as a doctoral candidate, an application for acceptance as a doctoral candidate must be submitted (you will find the form at the end of the Doctoral studies at the University of Tübingen webpage). The requirements are defined in § 3 of the PromO, details regarding the acceptance are defined in § 4 of the PromO.
Applications for acceptance as a doctoral candidate should be submitted before or immediately after starting your doctoral studies. In the past, there have been cases of applications submitted at a very late stage which for formal reasons could only be accepted conditionally or not at all. This should be avoided at all costs. In addition, according to IBMI's doctoral regulations, the TAC should be active from the first year on. Acceptance is also a necessary prerequisite for enrollment as a doctoral student at the University of Tübingen, which is mandatory since 30 March 2018 (see also the Doctoral studies at the University of Tübingen webpage).
During the study phase, each doctoral candidate is assigned at least two academic supervisors. At least one supervisor must be a full professor of the MNF or equivalent and a member of the Computer Science Department or the IBMI 1. Additional supervisors must belong to the group of people specified in § 4(5) of the PromO. Proposals for this so-called doctoral committee are made by the interested party, but these suggestions do not have to be accepted.