Simulation is common practice for surgeon training in particular for robotic surgery. This paper introduces further relevant applications of simulation that improve patient safety. Therefore, the design of a modular simulator for minimally invasive robotic surgery is presented. The authors introduce a classification of hierarchical levels of modeling details for the three aspects Application, System, and Patient. Furthermore, the principal use case classes Training, Workflow Validation, Workflow Design, Monitoring, and Robot Design of simulation for robotic surgery are introduced. For each class standard simulator setups are presented. The application of the classification is exemplified for the use cases Training and Robot Design.