Researcher

Microsoft Research Ltd

Stephen Robertson joined \Microsoft¤ Research Cambridge in April 1998. 
  

In 1998, he was awarded the Tony Kent STRIX award by the Institute of Information Scientists. In 2000, he was awarded the Salton Award by ACM SIGIR. He is a Fellow of Girton College, Cambridge. 
    

At Microsoft, he runs a group called Information Retrieval and Analysis, which is concerned with core search processes such as term weighting, document scoring and ranking algorithms, and combination of evidence from different sources. These are studied theoretically through the use of formal models, mainly statistical, and statistical methods including machine learning methods, and experimentally, through activities such as the Text Retrieval Conference (TREC) and with internally generated evaluation sets. The group (with its Keenbow evaluation environment) has had some excellent results at TREC. The group works closely with product groups to transfer ideas and techniques. 
      

His main research interests are in the design and evaluation of retrieval systems. He is the author, jointly with Karen Sparck Jones, of a probabilistic theory of information retrieval, which has been moderately influential. A further development of that model, with Stephen Walker, led to the term weighting and document ranking function known as Okapi BM25, which is used in many experimental text retrieval systems. 
  

Prior to joining Microsoft, he was at City University London, where he retains a part-time position as Professor of Information Systems in the Department of Information Science (homepage). He was Head of Department for eight years, during which time it achieved the highest possible rating in two successive research assessment exercises. He also started the Centre for Interactive Systems Research, the main research vehicle of which is the Okapi text retrieval system, which has also done well at TREC. 
   

Before joining City, he was a research fellow at University College London, where he took his PhD in the School of Library Archive and Information Studies. Before that he was in the research department at Aslib. He has an MSc in Information Science from City and a first degree in mathematics from Cambridge. 
    

A selected list of publications is here; slides of a talk given in November 1999 at Carnegie-Mellon University and the University of Pittsburgh, and some more from the ESSIR summer school in Varenna in September 2000. Papers on the Okapi and Keenbow systems at TREC are available here. The text of the Salton Award lecture is here. The Sparck Jones / Robertson IDF page is here. A large paper reviewing developments of our probabilistic models is here.