A Modular Object Oriented Data Acquisition System for the Gravitational Wave AURIGA Experiment

The new Data Acquisition system for the gravitational wave detector AURIGA has been designed from the ground up in order to take advantage of hardware and software platforms that became available in recent years; namely, i386 computers running Linux-based free software. This paper describes how advanced software development technologies, such as Object Oriented design and programming and CORBA infrastructure, were exploited to realize a robust, distributed, flexible, and extensible system. Every agent of the Data Acquisition System runs inside an heavyweight framework, conceived to transparently take care of all the agents intercommunication, synchronization, dataflow. It also presents an unified interface to the command and monitoring tools. The DAQ logic is entirely contained in each agent's specialized code. In the case of AURIGA the dataflow is designed as a three tier: frontend, builder, consumer. Each tier is represented by a set of agents possibly running on different hosts. This system is well fit for projects on scales comparable to the AURIGA experiment: permanent and temporary data storage is based on the Frame format adopted by the gravitational wave community, and the design is reliable and fault-tolerant for low rate systems.