He is also cofounder and director of ConfigWorks GmbH, a provider of interactive selling technology. His research interests focus on knowledge-based systems, particularly in the fields of interactive sales applications, such as product configuration and recommendation. He also works on knowledge acquisition and user modeling for personalization. He is an associate editor of the International Journal of Human-Computer Studies and he was co-chairing the program committee of the 4th ACM Conference on Recommender Systems in 2010. He is a co-author of the first introductory book on Recommender Systems that is published by Cambridge University Press.