Constructing Distributed Systems in Conic

Abslrucl-Existing distributed systems vary from those which merely provide interconnection of autonomous systems to those which provide a complete language environment for writing distributed programs. The former tend to support flexibility and provide ready access to system facilities, but suffer by being complex to use. Language environments are simpler to use and can provide safer environments by performing checks, but tend to be aimed a t constructing distributed programs rather than systems, and tend to hide and prevent access to many system level facilities. Both tend to be weak in their support for the configuration and modification of distributed applications. The Conic environment provides a language-based approach to the building of distributed systems which combines the simplicity and safety of a language approach with the flexibility and accessibility of a n operating systems approach. I t provides a comprehensive set of tools for program compilation, configuration, debugging and execution in a distributed environment. The environment is particularly strong in its conjigurution facilities. A separate Configuration language is employed to specify the configuration of software components into logical nodes. This provides a concise configuration description and facilitates the reuse of program components in different configurations. Applications a re constructed as sets of one or more interconnected logical nodes. Arbitrary, incremental change is supported by dynamic conjigurulion, the capability to dynamically create, interconnect, and control logical nodes. In addition, the system provides user transparent datatype transformation between heterogeneous processors. Applications may be run on a mixed set of interconnected computers running the UNIX@ operating system and on bare target machines with no resident operating system. This paper sets out the basic principles adopted in the construction of the Conic environment and, in particular, describes the configuration and run-time facilities provided. Examples a re used to illustrate the approach.