2007 - present Researcher at Yahoo! Research, Barcelona, focusing on Semantic Web technologies.

2002 - 2007 Ph.D. candidate) at the Business Informatics group of the Faculty of Sciences (FEW) at the Vrije Universiteit, Amsterdam.

His interdisciplinary work in the field of Social Networks and the Semantic Web earned a Best Paper Award at the International Semantic Web Conference in Galway, 2006 and a First Prize at the Semantic Web Challenge of 2005. He is also author of the book “Social Networks and the Semantic Web”, published in 2007 by Springer Verlag.

He has been involved in several large European Semantic Web projects such as On-To-Knowledge, SWAP (Semantic Web and Peer-to-Peer) and WonderWeb.

He is chief developer in a number of open source projects, including the Elmo API for the Sesame RDF store (see openrdf.org), openacademia.org and flink.semanticweb.org.

From November, 2005 he is a co-chair of the Semantic Web Challenge, together with Michael Uschold (2005) and Jennifer Golbeck (2006).

January–July, 2002 Worked as an intern at Aidministrator B.V., a Semantic Web start-up headquartered in Amersfoort, the Netherlands. During my internship I worked on the engineering of an ontology-based content management system as part of the European On-To- Knowledge research project.