In this paper, we start from observing the behavior of read_only logic variables which help clarify the mechanisms of Concurrent Prolog and then we illustrate two operational semantics for the read-only logic variables. We propose an operational model DDCS (Dynamic Distributed network of Centralized multiprocess System) for Concurrent Prolog programs, which succinctly combines the shared variables, message passing and remote-procedure-call schemes yet still preserves the object-oriented features of the centralized version. Using DDCS as the basis for a distributed Concurrent Prolog machine, we discuss the implementation issues and provide a simulation approach.