BNL, Upton, Long Island, New York
Stony Brook University, Stony Brook
Tech-X, Boulder, Colorado
CLASSE, Ithaca, New York
Data Distributed Service (DDS) from the Object Management Group represents the next generation of industrial middleware standards, bringing a data-centric publish-subscribe paradigm to distributed control systems. In comparison with existing middleware technologies, the data-centric approach is able to provide a consistent consolidated model supporting the different data dissemination scenarios and integrating many important issues, such as user-specific types, quality of service, data stream management and others. The paper highlights the different features of the DDS technology and introduces a prototype of the NSLS-II high level application environment including key middle layer servers, such as Machine, Online Model and Virtual Accelerator. The proposed environment is developed and evaluated on top of EPICS-DDS, an open source implementation of the DDS standard interface based on the EPICS Channel Access protocol (http://sourceforge.net/projects/epics-dds/).
Tech-X, Boulder, Colorado
As accelerators become bigger, traditional ways of building the control systems based on a single framework no longer scale. A Service-Oriented Architecture (SOA) adopting both RPC and a MOM standard service buses promotes multiple levels of loose coupling to increase the robustness and adaptability of overall control applications without sacrificing performance. The emerging OMG DDS specification defines a data-centric communication standard with rich supports for quality-of-service. It is especially suited as the SOA's MOM service bus for control systems. DDS helps extend the real-time data available from the proven control development framework such as EPICS, as standard services and data exchanges between services in a SOA environment. In this paper, we review various features in the OMG DDS standards and their applications in control applications. We also illustrate how, collaborating with Web Services, DDS fits into a SOA for accelerator control systems. Finally, we present and evaluate performance benchmarking results of several DDS implementations, including an EPICS-DDS, which is an open source implementation of OMG DDS.