The DELPHI experiment control system

DELPHI (DEtector with Lepton, Photon and Hadron Identification) is one of the four experiments built for the LEP (Large Electron-Positron) collider at CERN. The DELPHI detector is composed of 20 subdetectors, which were built by different teams of laboratories of the DELPHI collaboration. The control system of the experiment has to assure the correct and continuous operation of the experiment until around the year 2000 and it has to allow for an easy reconfiguration in order to cope with the replacement and upgrades of the different parts of the experiment during its live time. The control of a physics experiment involves multiple domains with different requirements (some parts have to work in real-time, some are safety critical, others have to be user-friendly). Usually these domains are engineered separately. In order to increase the operating efficiency and the reliability and maintainability of the system DELPHI took a global approach in the design of the complete experiment control. This approach allowed for the interconnection of the various domains and led to a high degree of automation and an homogeneous interface to the full control system. This paper describes the strategy adopted in order to handle the different and sometimes contradictory requirements of the different parts of the system keeping thus an overall system perspective