The authors present a conceptual framework for the organization of services 
in distributed systems out of collections of participating servers. The 
approach is based on the notion of service layer inserted between the 
distributed operating system kernels and client-server objects. A service 
layer consists of disjoint sets of service agents. The authors demonstrate 
that this approach favors the development of transparent distributed services 
which hide the server structure from both clients and servers and encapsulate 
nonfunctional issues of a service such as load distribution or fault 
tolerance, within the cooperation protocol established between cooperating 
service agents. Thus the proposed scheme may be viewed as a generalized 
framework for modeling arbitrary distributed services, such as a distributed 
file service.