Applications of CORBA in the atlas prototype DAQ

This paper presents the experience of using the Common Object Request Broke r Architecture (CORBA)[1] in the ATLAS prototype DAQ project[2]. Many commu nication links in the DAQ system have been designed and implemented using t he CORBA standard. A public domain package, called Inter-Language Unification (TLU)[3] has bee n used to implement CORBA based communications between DAQ components in a local area network (LAN) of heterogeneous computers. The CORBA Naming Service[4] provides the principal mechanism through which most clients of an ORE-based system locate objects that they intend to use. In our project, conventions are employed that meaningfully partition the n ame space of the Naming Service according to divisions in the DAQ system it self. The Inter Process Communication (IPC) package[5], implemented in C+on the top of CORBA/ILU, incorporates this facility and hides the details o f the naming schema is described. The development procedure and environment for remote database access using IPC is described. Various end-user interfaces have been implemented using the Java language t hat communicate with C++ servers via CORBA/ILU. To support such interfaces, a second implementation of IPC in Java has been developed. The design and implementation of such connections are described. An alternative CORBA implementation, ORBacus[6], has been evaluated and com pared with ILU.