Applications of CORBA in the ATLAS prototype DAQ

This paper presents the experience of using the Common Object Request Broker Architecture (CORBA) in the ATLAS prototype DAQ project. Many communication links in the DAQ system have been designed and implemented using the CORBA standard. A public domain package, called Inter-Language Unification (ILU) has been used to implement CORBA based communications between DAQ components in a local area network (LAN) of heterogeneous computers. The CORBA Naming Service 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 name space of the Naming Service according to divisions in the DAQ system itself. The Inter Process Communication (IPC) package, implemented in C++ on the top of CORBA/ILU, incorporates this facility and hides the details of 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 that 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, has been evaluated and compared with ILU.