[en] Offline Software such as Simulation, Reconstruction, Analysis, and Visualisation are all in need of a detector description. These applications have several common but also many specific requirements for the detector description in order to build up their internal representations. To achieve this in a consistent and coherent manner a common source of information, the detector description database, will be consulted by each of the applications. The role and suitability of XML in the design of the detector description database in the scope of the CMS detector at the LHC is discussed. Different aspects such as data modelling capabilities of XML, tool support, integration to C++ representations of data models are treated and recent results of prototype implementations are presented