On the use of modifiers for real-time execution in MMS

Manufacturing message specification (MMS) is an application layer protocol developed by ISO to address the problem of factory communications. MMS is part of the manufacturing automation protocol (MAP) project initiated by General Motors whose scope is to promote interoperability among heterogeneous industrial devices and more conventional computers. Concerns for real-time requirements is a key issue if MMS is to be widely adopted in industrial plants. This article presents solutions for controlling the service time of a request, i.e. the total time a request spends in an MMS server. We show that it is possible to achieve real-time execution in MMS without modifying the MMS protocol. These solutions are based on MMS modifiers