Control in the ATLAS TDAQ System

TDAQ system requires a comprehensive and flexible control system. Its role ranges from the so-called run-control, e.g. starting and stopping the data taking, to error handling and fault tolerance. It also includes initialization and verification of the overall system. Following the traditional approach a hierarchical system of customizable controllers has been proposed. For the final system all functionality will be therefore available in a distributed manner, with the possibility of local customization. After a technology survey the open source expert system CLIPS has been chosen as a basis for the implementation of the supervision and the verification system. The CLIPS interpreter has been extended to provide a general control framework. Other ATLAS Online software components have been integrated as plug-ins and provide the mechanism for configuration and communication. Several components have been implemented sharing this technology. The dynamic behavior of the individual component is fully described by the rules, while the framework is based on a common implementation. During this year these components have been the subject of scalability tests up to the full system size. Encouraging results are presented and validate the technology choice.