A distributed data processing system having several local systems (LS) between which communication is provided via clearly defined functional layers. A functional coordination layer managed by systems intercommunication processors (SIP) is responsible for the functions of coordination, communication, control, initialization and simulation relative to the LSs. A functional communication layer managed by communication modules (CM) is responsible for the communication protocols between the LSs. A functional transport layer including transmission modules (TM), a looped optical bus and a looping unit (LIG) element. A description of each LS is contained in its SIP in the form of descriptive tables facilitating the use of the resources of the global system by any LS via parameter translations, local to global to local, each communication between LSs being performed in the form of a transaction having separate interrogation, auto-selection, presentation, processing and result return phases.