Bonnie John is Professor of HCI at Carnegie Mellon University. An early contribution was applying cognitive modeling techniques to predict human-computer interaction in a new telephone operator console system. This innovative work correctly predicted that the company's new system for operators would actually increase call-handling time over the that used in the old system. Bonnie has since applied cognitive modeling to many complex real world tasks, such as analyzing usability problems in Web browsing and automobile driving. She also invented new modeling methods (in particular CPM-GOMS) that are more efficient and better adapted to complex tasks than previous methods. Understanding that novices have difficulty modeling, Bonnie made strides in making cognitive modeling more accessible to researchers and engineers. Her pairing of empirical science with cognitive modeling for usability evaluation is a major contribution to the field, and has inspired many other researchers. Bonnie's evaluation studies are some of the most precise and quantitative analyses in our field. She routinely publishes influential articles on evaluation techniques that foster debate in the HCI world. In recent years, Bonnie also has done groundbreaking research to integrate the analysis of usability problems with the standardized engineering process.