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 This facilitates timely responses to new and outdated information.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 portals.omg.org/dds/. 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