GAUDI - A software architecture and framework for building HEP data processing applications

We present a software architecture and framework that can be used to facilitate the development of data processing applications for High Energy Physics experiments. The development strategy follows an architecture-centric approach as a way of creating a resilient software framework that can withstand changes in requirements and technology over the long lifetimes of experiments. The software architecture, called GAUDI, supports event data processing applications that run in different processing environments, from the high level triggers in the on-line system to the final physics analysis. We present our major architectural design choices and outline the arguments that led to these choices. Several iterations of a software framework based on this architecture have been released and the framework is now being used by the physicists of the collaboration to facilitate the development of data processing algorithms. Object oriented technologies have been used throughout. (C) 2001 Elsevier Science B.V. All rights reserved.