Promotion in my own interest: the handbook “Datenrecht in der Digitalisierung” (Data Law in Digitalisation), edited by Louisa Specht-Riemenschneider, Nikola Werry and Susanne Werry, is now available. It is a very opulent volume, which in the end only just misses the 1,000 page mark. Not that the mere number of pages matters: But more than 30 authors deal with different legal and sociological aspects of information society law. And after all 42 (the answer to the question of all questions) of these pages are from me and deal with very important topics of my scientific and practical work. Under the title “Market power through data – an analysis from a legal perspective”, I do not only present current controversial issues of market definition and market power analysis for digital platforms. Thus, I am also attempting a practice-related analysis of the structural criteria in Section 18 (3a) ARC, which were included in the 9th amendment to the ARC in 2017, for determining the dominant position in “multilateral markets and networks” It also deals with the consequences especially in connection with the prohibition of abusive practices and the general ban on coordinated practises. In this context, it is necessary to take a differentiated view of the data as possible access objects. And with all the focus on data, it must be equally clear that in many cases it is not just this data that is important, but also any further obligations to cooperate or infrastructures. In German law, this can be well illustrated in connection with the concept of relative market power.