Applications of CORBA in the Atlas prototype DAQ

This paper prescnts tlic cxpericnce of using the Common Object Requcst Broker Architecture (CORBA)[ I] in tlic ATLAS prototype DAQ project[2]. Many coiiiniunication links in the DAQ systcm have been dcsigned and implcmentcd using thc CORBA standard. A public domain package, callcd Inter-Language Unification (ILU)[3] has bccn used to implement C O R M based communications between DAQ componcnts in a local arca network (LAN) of hetcrogcncous computers. The CORBA Naming Service[4] provides the principal mechanism through which most clicnts of an ORB-bascd systcm locate objccts that they intend to iisc. In our project, conventions arc employed that meaninglhlly partition the namc space of the Naming Servicc according to divisions in thc DAQ system itself. The Inter Proccss Communication (IPC) package[5], implcmented in C-I-t 011 thc lop of CORBAIILU, incorporates this facility and hides tlie details of the naming schcnia is described. Thc devclopment proccdure and environment for rcmotc databasc access using IPC is described. Various end-user intersaccs have bcen iinplcmentcd using thc Java language that communicatc with C t t servers via CORBAIILU. To support such intcrfaccs, a second implemcntation of II'C in Java has been developed. Thc design and implementation of such connections are dcscribcd. An altcrnative CORBA impleincntation, ORRacus[b], lias bccn evaluatcd and compared with ILU.