Design of hierarchical control framework for ALICE online and offline system

This paper presents the design and implementation of the ALICE O2 Control System prototype. The design of our system is based on the ALICE O2 requirements. The system allows the crew operating the experiment to send simple commands in order to control the ongoing processes running in the computing farm. The sent command is capable of reacting to changing conditions and operational the requirements of experiments' processes. The system supports general commands such as pausing or resuming an ongoing activity, applying a new configuration or terminating the current operation and moving it to a standby status. The topics learnt from this study include communication patterns, multi-level communication, distributed systems as well as state machine controlling. The system is based on the C++ programming language.