The Message Reporting System (MRS) in the ATLAS data acquisition system (DAQ) is one package of the Online Software which acts as a glue of various elements of DAQ, High Level Trigger (HLT) and Detector Control System (DCS). The aim of the MRS is to provide a facility which allows all software components in ATLAS to report messages to other components of the distributed DAQ system. The processes requiring a MRS are on one hand applications that report error conditions or information and on the other hand message processors that receive reported messages. A message reporting application can inject one or more messages into the MRS at any time. An application wishing to receive messages can subscribe to a message group according to defined criteria. The application receives messages that fulfill the subscription criteria when they are reported to MRS. The receiver message processing can consist of anything from simply logging the messages in a file/terminal to performing message analysis. The inter-process communication is achieved using the CORBA technology. The design, architecture and the used technology of MRS are reviewed in this paper
