The subject of the doctoral project is the textual structure of the libri ad Sabinum by the late classical Roman jurist Domitius Ulpianus (‘Ulpian’) – a work of Roman legal literature that is ‘commenting’ on Massurius Sabinus’ libri tres iuris civilis. The investigation is not based on Ulpian's entire commentary work, which has come down to us in 51 books. Instead, the internal context is reconstructed using the 32nd book ad Sabinum as an example. It is a much-discussed text in Roman law studies that deals with the prohibition of gifts between spouses and contains many complex decisions. Quite a few of them still raise problems of interpretation today.

The question of text structure addresses the relationship between Sabinus' textbook and Ulpian's ‘commentary’: Although the libri ad Sabinum are undoubtedly related to the systematic presentation of Sabinus, and are therefore ‘heteronomous’, it is not clear how close this frame of reference to their pretext actually is – and whether Ulpian himself oriented only on the structure of his template, but developed the individual sections of the libri on the basis of his own systematization approaches and ordering schemes, or rather wrote a lemmatic commentary, which always starts with a quote from Sabinus, dissects it and annotates it word for word. The research objective of the work is to measure this ‘distance’ between the Sabinus commentary and its pretext, i.e. to determine the extent of ‘autonomy’ that the libri ad Sabinum could have developed despite the orientation towards the Sabinus textbook.

Textbook and commentary have not been handed down in their original form, but are known through the legislative work of the Byzantine Emperor Justinian I, the Corpus Iuris Civilis. On the basis of the source material, the legal historian Otto Lenel has reconstructed many classic texts in his Palingenesia Iuris Civilis and thus paved the way for an in-depth examination of the 32nd book ad Sabinum.