Data distribution service for real-time systems (DDS) is a specification of a publish/subscribe middleware for distributed systems created by the Object Management Group (OMG) in response to the need to standardize a data-centric publish-subscribe programming model for distributed systems.
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A few proprietary DDS solutions had been available for several years. Starting in 2001, two major DDS vendors, the American group Real-Time Innovations and the French Thales Group teamed up to create the DDS specification in and which was subsequently approved by the Object Management Group resulting in Version 1.0 in 2003.
Version History
The DDS specification describes two levels of interfaces:
DDS is networking middleware that simplifies complex network programming. It implements a publish/subscribe model for sending and receiving data, events, and commands among the nodes. Nodes that are producing information (publishers) create "topics" (e.g., temperature, location, pressure) and publish "samples." DDS takes care of delivering the sample to all subscribers that declare an interest in that topic.
DDS handles all the transfer chores: message addressing, data marshalling and demarshalling (so subscribers can be on different platforms than the publisher), delivery, flow control, retries, etc. Any node can be a publisher, subscriber, or both simultaneously.
The DDS publish-subscribe model virtually eliminates complex network programming for distributed applications.
DDS supports mechanisms that go beyond the basic publish-subscribe model. The key benefit is that applications that use DDS for their communications are entirely decoupled. Very little design time has to be spent on how to handle their mutual interactions. In particular, the applications never need information about the other participating applications, including their existence or locations. DDS automatically handles all aspects of message delivery, without requiring any intervention from the user applications, including:
This is made possible by the fact that DDS allows the user to specify Quality of Service (QoS) parameters as a way to configure automatic-discovery mechanisms and specify the behavior used when sending and receiving messages. The mechanisms are configured up-front and require no further effort on the user's part. By exchanging messages in a completely anonymous manner, DDS greatly simplifies distributed application design and encourages modular, well-structured programs.
DDS also automatically handles hot-swapping redundant publishers if the primary fails. Subscribers always get the sample with the highest priority whose data is still valid (that is, whose publisher-specified validity period has not expired). It automatically switches back to the primary when it recovers, too.
DDS is available from different vendors with Ada, C, C++, C#, and Java APIs, as well as Open-source software.
Space Software Italia developed a JAVA DDS version for applications based on Fixed and Mobile Cooperating Multi-Agents (Swarm Systems)