Generative and evaluative approaches are two different ways of diagnosing students’ input that have been realized in a number of intelligent tutoring systems. We describe how ActiveMath’s exercise subsystem realizes both types of diagnosis and how it can combine them. A framework for distribution of diagnostic services is extending the existing web-service approach to mathematical services with the notion of context. In addition to an appropriate diagnosis, a goal is the interoperability of diagnosis services. Keywords. diagnosis, evaluative and generative approach, user modeling, interoperability