He has a broad knowledge on topics related to the management of data and databases. His specific areas of expertise in this context focus on data on the Semantic Web and on graph data, as well as on problems of federated data management in which data is distributed over multiple, autonomous and/or heterogeneous data sources. Regarding these topics, Olaf's interests range from systems-building related research all the way to theoretical foundations. Olaf presented several tutorials at top international conferences in the Semantic Web area including WWW (2010, 2013, 2017) and ISWC (2008, 2009, 2017), and he was lecturer at the 2011 Indian-Summer School on Linked Data.