Service-oriented architecture for distributed publish/subscribe middleware in electronics production

The Computer Aided Manufacturing using XML (CAMX) framework enables integrating electronics production systems using message-oriented middleware, offering standards-based communication among machines and control software applications. CAMX frameworks implement publish/subscribe of XML messages through an entity called the message broker (MSB), which provides the messaging service using a web-based interface. A challenge for MSB-based systems is that they must scale to handle large volumes of messaging traffic, which is a characteristic of modern information-intensive manufacturing systems. This paper first tackles this challenge by presenting an array of architecture patterns for creating distributed MSB frameworks, focusing mainly on globally distributed federations and locally distributed clusters. A unified architecture is subsequently presented that leverages the different patterns by combining federated frameworks with locally distributed clusters into a unified set of architecture elements and interactions. A service-oriented approach is followed to provide a uniform interface for distributed MSB elements, whether federated or locally distributed. The service-oriented approach is also used to dynamically discover resources and automatically invoke the (re)configuration and messaging services. The services are enriched with semantics in order to facilitate automatic discovery and selection of services using the semantic web services formal ontology. Semantic service advertisements are propagated using a peer-to-peer discovery protocol. The approach presented in this paper is not limited to the CAMX case and is generally applicable to distributed event-based manufacturing systems.