Cool: an Object Support Environment Co-existing with Unix

1 Abstract The COOL 1 system has been designed to satisfy two goals; to provide an eecient object oriented support layer built directly on the Chorus Micro-Kernel and to co-exist with UNIX by ooering access paths, and by using Unix functionality. In this paper we discuss how the COOL system has been designed to exploit features of the Chorus operating system model, to provide abstractions suited to object oriented systems. A signiicant feature of the COOL project is that we have been able to exploit the design methodology of Chorus to allow COOL to co-exist with the Chorus Unix implementation (MiX) Armand89] yet still build our abstractions directly onto the Chorus Nucleus, exploiting its eeciency and functionality. To demonstrate the feasibility of this approach and to gain experience of our abstractions, we have built a C++ environment on the COOL subsystem that enables programmers to develop applications consisting of standard C++ objects that can then be used in a transparent manner in a distributed environment. This has been carried out in conjunction with SEPT 2 as part of the CIDRE project and is reported in Deshayes89] We describe a number of developments with this C++ environment, including experiments to support a single invocation model based on the ANSA RPC package Esprit89] and utilising the COOL object migration facilities. From this work we outline a number of drawbacks of the COOL model and present our future directions of research.