The offline software framework of the Pierre Auger Observatory

The Pierre Auger Observatory is designed to unveil the nature and the origin of the highest energy cosmic rays through the detection of extensive air showers, using a hybrid fluorescence/surface array detector. It will consist of two sites, one currently under construction in Argentina and another pending in the Northern hemisphere. Each site comprises a ground array of approximately 1600 water Cherenkov tanks overlooked by four atmospheric fluorescence detectors. The large and geographically dispersed collaboration, and the heterogeneous set of simulation and reconstruction requirements pose some special challenges to the offline software design. We have designed and implemented a framework to allow collaborators to contribute algorithms and sequencing instructions to build up the variety of applications they require. The framework includes machinery to manage client code, to organize the abundance of user-contributed configuration files, to facilitate multiformat file handling, and to provide access to event and time-dependent detector information which can reside in various data sources. The framework is implemented in C++, follows an object oriented paradigm, and takes advantage of some of the more widespread tools that the open source community offers, while keeping the client-side simple enough for C++ non-experts.