DDS™ - The Proven Data Connectivity Standard for IoT™ Nov. 2016 - Page 9

UNDERLYING TECHNICAL CONCEPTS data by both structure related topics (using key-fields) and allow ad-hoc queries and filters on content and time so applications can extract specific data as needed. • Pub-sub messaging: DDS uses the publish/subscribe paradigm for dynamic discovery and primary management of data-flows between relevant DDS entities, including publishers, subscribers, durability services, recording and replay-services, and connected databases. Request-reply and other patterns are built on this powerful substrate. • Reliable multicast: The DDS standard wire protocol implements reliable multicast over plain UDP sockets, allowing systems to efficiently benefit from modern networking infrastructures. • Lifecycle awareness: Unlike message-centric products, DDS offers explicit application support for infor- mation lifecycle awareness. For instance, it detects, communicates, and informs applications about first and last appearances of data (topic instance) updates. This facilitates timely responses to new and outdated information. • Trigger patterns: DDS offers a variety of trigger patterns that follow updates on subscribed information. Examples include polling, callbacks (typical for GUIs), and WaitSets (similar to UNIX® ‘select’ ) to provide full application control for prioritized handling of selective trigger events. You can find more information on DDS and how it works at Getting four complex robots with very different designs to use a common data system was challenging. The Data Distribution Service for Real-Time Systems [DDS] standard supports very flexible service parameters. We found that we could adapt the middleware to the unique needs of each robotic system.” - Terry Fong, Director of Intelligent Robotics Group, NASA Ames 9 HOW DOES DDS WORK? • Relational data modeling: DDS addresses data in a manner similar to relational databases. It can manage