RTMMS—An OSI-based real-time messaging system

Abstract

A critical component of the MAP initiative has been the development of a message handling system—initially designed for manufacturing environments—termed MMS. In terms of the OSI model, this application-layer system is designed to support communications to and from programmable devices, specifically in manufacturing, and, more recently, in process-control environments as well. MMS also permits specific, application-oriented messaging systems to be built around the core definition of MMS—these additional systems being termed companion standards. However, although dedicated to such real-world environments, MMS does not have a direct capacity to support time-critical services. It has been recognized that such capabilities are vital in many areas of control, and therefore work needs to be undertaken to extend MMS to cover this field. This paper addresses some of the issues where MMS, in its standardized form, falls short, and suggests what can be done to overcome these difficulties. It proposes additions to the MMS profile, and basically, therefore, to the Virtual Manufacturing Device which underlies the MMS system. In the context of the paper, it should be noted that Real-time MMS is not designed as a replacement for the Manufacturing Messaging Specification, but rather functions alongside it. The paper concludes by illustrating how such real-time extensions may be implemented.