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 This facilitates timely responses to new and outdated information.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