Sommer, H.

Paper	Title	Page
WEA006	Data Distribution Service as an Alternative to CORBA Notify Service of the ALMA Common Software	373
	J. A. Avarias NRAO, Socorro, New Mexico G. Chiozzi, H. Sommer ESO, Garching bei Muenchen
	The ALMA Common Software (ACS) provides the infrastructure for the Atacama Large Millimeter Array and other projects. ACS, based on CORBA, offers basic services and common design patterns. One of these services is the Notification Channel. Based on the CORBA Notify Service, it allows the implementation of applications based on the publisher-subscriber pattern. This is very useful for handling asynchronous messages between components, and fosters data-centric architectures and de-coupling between different components of an application. The Notify Service has several limitations, such as being resource intensive and not scaling well with the number of subscribers. The Data Distribution Service (DDS) provides an alternative standard for publisher-subscriber communication for real-time systems, offering better performance and featuring decentralized message processing, scalable peer-to-peer communication, and a wide set of QoS policies. We describe the integration of DDS into the ACS CORBA environment, replacing the Notify Service. Benefits and drawbacks are analyzed. A benchmark is presented, comparing the performance of both implementations.
TUP101	ALMA Common Software (ACS), Status and Development	313
	G. Chiozzi, A. Caproni, B. Jeram, J. Schwarz, H. Sommer ESO, Garching bei Muenchen J. A. Avarias NRAO, Socorro, New Mexico R. Cirami INAF-OAT, Trieste A. Grimstrup University of Calgary, NW Calgary, Alberta A. A. Hoffstadt, J. S. Lopez UTFSM, Valparaíso M. Sekoranja Cosylab, Ljubljana N. Troncoso ALMA, Joint ALMA Observatory, Santiago H. Yatagai NAOJ, Tokyo
	ACS provides the infrastructure for the software of the Atacama Large Millimeter Array and other projects. Using CORBA middleware, ACS supports the development of component-based software, from high-level user interfaces down to the hardware device level. It hides the complexity of CORBA beneath an API that allows the application developer to focus on domain-specific programming. Although ACS, now at release 8, has been used operationally by the APEX radio telescope and at the ALMA Test Facility, the commissioning of ALMA in Chile brings major challenges: new hardware, remote operation and, most important, upscaling from 2 to 60+ antennas. Work now turns to scalability and improving the tools to simplify remote debugging. To further identify potential problems, the University of Eindhoven is formally analysing ACS. Meanwhile, new developments are underway, both to respond to newly identified needs of ALMA, and those of other projects planning to use ACS. Examples include the refactoring of the interface to the CORBA Notify Service, integration with the Data Distribution Service, generation of state machine code from abstract models and of Python binding classes from XML schema.
	Poster