In this position paper, we propose a new generation workflow system for grid services. We observe that grid computing has become an increasingly important application domain in computer science. Grid services — a new technology based on web services — are expected to become the de facto standard for grid computing. Similar to web services, an effective mechanism is needed for the composition of grid services. Existing technologies, however, have a number of important drawbacks: they have limited or no support for modularization of crosscutting concerns, for dynamic workflow adaptation, and for high-performance computing. We propose a new generation workflow system that is tailored specifically for grid services, and that tackles these problems, among others.