In my research I am interested in applying techniques from automated theorem proving, logic, and complexity theory to knowledge representation and reasoning, and in particular for reasoning in description logics and ontology languages. The topics of my works are quite diverse. I have been working with Hans de Nivelle on the development of resolution-based procedures for various fragments of first-order logic, with Boris Motik on resolution-based procedures for description logics, and with Bernardo Cuenca Grau, Ian Horrocks and Ulrike Sattler on the topic of modularity in ontolgies. Recently, I have been working with Birte Glimm on role conjunctions in expressive description logics, and with Ian Pratt-Hartmann on complexity of graded modal logics. The primary focus of my current work is consequence-based ontology reasoning procedures. I develop a prototype reasonesr CB and ELK based on such procedures.