Ian Foster of the U.S. Department of Energy's Argonne National Laboratory has been recognized as one of the top three most influential computer scientists worldwide, according to a new formula that measures the impact of a scientist's work. According to the h-index, a method for ranking scientists based on the number of papers they publish and citations they receive, Foster ranks third with a score of 67. Featured in the August 16 issue of Nature, the h-index indicates the number of papers a particular author publishes that receive at least that same number of citations; thus, Foster's score of 67 means that he has published 67 papers that have received at least 67 citations apiece. The world's leading computer scientist, by this scale, has a score of 70. "It's nice to realize that when I write papers people will read them, and that I have some influence," Foster said. "Presumably, my score represents the broad interest in my field." However, Foster's modesty prevented him from assigning a great deal of weight to the h-index. "I think it says a little more about the limitations of these numerical scores than anything," he said of his ranking. "It's a pluralist way of defining a scientist's reputation, while the more commonly-used mechanism for that is to rely on the opinions of other experts in the field. But numbers can serve some purpose as another way of evaluating things." Foster, known as the "father of grid computing," is associate division director for Argonne's Mathematics and Computer Science Division and is also Arthur Holly Compton Distinguished Service Professor of Computer Science at The University of Chicago. He has received the Lovelace Medal of the British Computer Society and the Gordon Bell Prize for high-performance supercomputing. Foster currently works as the director of the Computation Institute, a joint project between Argonne and The University of Chicago and tackles the most difficult computational and communications problems that hinder scientists in many different disciplines. Research at the Computation Institute can provide solutions in any field that requires intensive computing capabilities, including disease diagnosis, weather forecasting and aircraft design simulation.