Databases: query languages, relational, XML, and graph data, constraints and design, data integration and exchange, incomplete information, etc.
Logic in computer science, finite model theory, automata theory
In the past: lattice theory, with some applications to programming semantics.

Leonid Libkin is Professor of Foundations of Data Management in the School of Informatics at the University of Edinburgh. He was previously a Professor at the University of Toronto and a member of research staff at Bell Laboratories in Murray Hill. He received his PhD from the University of Pennsylvania in 1994. His main research interests are in the areas of data management and applications of logic in computer science. He has written four books and over 200 technical papers. He was the recipient of a Marie Curie Chair Award from the EU in 2006 - 2009, a Premier's Research Excellence Award in 2001, and won five best paper awards. He has chaired programme committees of major database conferences (ACM PODS, ICDT) and was the conference chair of the 2010 Federated Logic Conference. He has given many invited conference talks and has served on multiple program committees and editorial boards. He is an ACM fellow, a fellow of the Royal Society of Edinburgh, and a member of Academia Europaea.