I am interested in problems related to the management of data and databases. My focus in this broad context is on data on the Web (Semantic Web and Linked Data, in particular) and on graph data, as well as on problems in which the data is distributed over multiple, autonomous and/or heterogeneous sources (keyword: federated data management). Other keywords that appear in some of my work are data provenance and data quality. Regarding all of these topics, my interests range from systems-building related research (e.g., efficient storage of datasets and databases, query processing, and query optimization) all the way to theoretical foundations (e.g., complexity and expressive power of query languages).