He joined the faculty in the Department of Computing Science at University of Aberdeen in 2005. He is now the Deputy Director of Research of the department. His research focuses primarily on knowledge representation and reasoning, in particular scalable ontology reasoning, querying and reuse, and their applications (such as Semantic Web, Advertising, Healthcare, Software Engineering and Multimedia). He is a key contributor to the W3C OWL2 standard. He leads the work of the TrOWL Tractable OWL2 reasoning infrastructure. He is widely recognised for his work on scalable and efficient ontology reasoning; he gave tutorials on this topic in e.g. AAAI2010, ESWC2010, ESWC2011, SemTech2011 and the Reasoning Web Summer School (2010 and 2011).