Simulation framework and XML detector description for the CMS experiment

Currently CMS event simulation is based on GEANT3 while the detector description is built from different sources for simulation and reconstruction. A new simulation framework based on GEANT4 is under development. A full description of the detector is available, and the tuning of the GEANT4 performance and the checking of the ability of the physics processes to describe the detector response is ongoing. Its integration on the CMS mass production system and GRID is also currently under development. The Detector Description Database project aims at providing a common source of information for Simulation, Reconstruction, Analysis, and Visualisation, while allowing for different representations as well as specific information for each application. A functional prototype, based on XML, is already released. Also examples of the integration of DDD in the GEANT4 simulation and in the reconstruction applications are provided.