Persistent shared object support in the Guide system

The purpose of the Guide project is to explore the use of shared objects for communication in a distributed system, especially for applications that require cooperative work. Since 1986, two prototypes have been implemented respectively on top of Unix (Guide-1) and Mach 3.0 (Guide-2). They have been used for the development of distributed cooperative applications, allowing us to validate or reject many design choices in the system. This paper gathers the lessons learned from our experience and compares the basic design choices with those in other distributed object-oriented systems. The lessons may be summarized as follows. This system layer must provide a generic interface for the support of several object-oriented languages. It must manage fine grained objects and enforce protection between objects and processes. These requirements can be achieved with an acceptable trade-off between protection and efficiency.