Decoupled System Architecture

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DDS supports a unique data-centric approach to system design. Most distributed-system designers build a tightly connected web of clients and servers. When you need to add a new component, you have to rework all the interfaces to existing components. Startup and shutdown sequences become tightly coupled and very brittle. Losing or overloading a key server can cause total system failure.

In contrast, DDS designers build a clean publish-subscribe data bus. There are no special nodes and thus no bottlenecks or coupled startup or shutdown procedures. Components can join or leave at any time without rework. (And at the same time, you'll be lowering your hardware and administration costs by eliminating those server machines.)

DDS is the only publish-subscribe technology that offers this level of decoupling. What's the secret? DDS allows components to specify—to the level of detail you decide—what their communication requirements are on a per-data-stream basis. The middleware then matches data producers and consumers that have compatible demands—dynamically and automatically.

This level of modularity and Quality of Service (QoS) control is unprecedented; it allows designers to build components independent of their eventual use in a system, increasing software reuse and decreasing integration time. It's just one of the reasons that the U.S. Navy has mandated the use of DDS technology for shipboard communications as part of its Open Architecture initiative and why RTI Data Distribution Service was selected to provide the real-time data-distribution infrastructure for Aegis Open Architecture (AOA), the next generation of the Aegis Weapon System.

Open Architecture, Open Systems

RTI Data Distribution Service provides an open architecture: one in which standards-based protocols and interfaces allow you to integrate with a system even if that system was not designed with your new component in mind.

In a DDS-based system, that protocol is RTPS (Real-Time Publish-Subscribe), and those interfaces are the structural and behavioral requirements of each component, that is, their data types and quality-of-service configurations. These structural and behavioral contracts are explicit, first-class citizens in the design of a DDS-based system, which brings several benefits in addition to streamlined system integration:

• Separate the jobs of (a) determining what data to send when from (b) tuning how to send it (for example, with what level of reliability or availability). Reconfigure a component pre- or post-integration without having to touch its code or redeploy it.
• Let RTI Data Distribution Service check compatibility for you and notify you if two components won't be able to communicate properly.
• Inspect and debug configurations during development or deployment with tools such as RTI Analyzer.
• Seamlessly integrate with third party applications and tools, such as Microsoft Excel for live data analysis and visualization or an Oracle database for large-scale data management.

Other communication technologies not only couple components tightly; they couple them implicitly, with no ability to detect or audit problems before integration and deployment. They cannot offer these benefits.

In the words of Peter Justesen, head of Simulation and Information Technologies at Force Technology, a market leader in the design of multi-ship simulator systems, "The publish-subscribe paradigm of DDS enables systems to share data without having to create unique interfaces for each system. It therefore frees our developers from needing to know the internal operation of each subsystem in order to retrieve its data. All the application needs to do is to subscribe to the desired data sets and DDS does the rest."

Continue reading to learn more about the groundbreaking performance and scalability of RTI Data Distribution Service…