On the scheduling of MMS services

The manufacturing message specification (MMS) was developed to deal with the problem of proprietary communication protocols and incompatible manufacturing devices found in industrial applications. In this paper we briefly present a state model for the execution of MMS services that allows to better understand how services are dealt with in MMS servers. This model is then used to propose an extension to MMS. With this extension MMS services can be given priorities and can be scheduled for execution in MMS servers according to these priorities. The assignment of priorities to services is not considered in the MMS standard. Our solution has the advantage of avoiding any modification to the MMS protocol and remains compatible with existing MMS applications. This study is a step in the direction of providing real-time MMS servers, a critical issue not well understood yet.