CMS software architecture - Software framework, services and persistency in high level trigger, reconstruction and analysis

This paper describes the design of a resilient and flexible software architecture that has been developed to satisfy the data processing requirements of a large HEP experiment, CMS, currently being constructed at the LHC machine at CERN. We describe various components of a software framework that allows integration of physics modules and which can be easily adapted for use in different processing environments both real-time (online trigger) and offline (event reconstruction and analysis). Features such as the mechanisms for scheduling algorithms, configuring the application and managing the dependences among modules are described in detail. In particular, a major effort has been placed on providing a service for managing persistent data and the experience using a commercial ODBMS (Objectivity/DB) is therefore described in detail. (C) 2001 Elsevier Science B.V. All rights reserved.