Real-time middleware meets new DDS standard

NDDS (Network Data Distribution Service), RTI's publish-subscribe middleware, is now available based on the Object Management Group's (OMG) Data Distribution Service (DDS, V1.0).

NDDS (Network Data Distribution Service), RTI's publish-subscribe middleware, is now available based on the Object Management Group's (OMG) Data Distribution Service (DDS, V1.0).

The DDS specification standardises the software application programming interface (API) and underlying communications model a developer can use to create distributed applications.

DDS is based on the simple, yet powerful, data-centric publish-subscribe (DCPS) communications paradigm that offers the application developer a high level of abstraction and yet controls all the quality of service (QoS) parameters needed for deploying real-time systems.

RTI's NDDS publish-subscribe middleware has been integrated with the DDS API.

This commercial-off-the-shelf (COTS) implementation offers a high-degree of fault tolerance while reducing schedule risks, initial development costs and total cost of system ownership.

NDDS also provides greater flexibility in terms of platforms, languages and transport mechanisms.

NDDS' robustness and flexibility are critical to distributed real-time systems such as simulators, telecommunications, industrial automation, medical equipment, factory automation and avionics.

"The finalisation and availability of the DDS specification really is a tremendous achievement that addresses a significant need in both the government and civilian commercial sectors", noted Dr Richard Soley, Object Management Group's Chairman and Chief Executive Officer.

"The DCPS model stands as a natural complement to the object-centric client-server model provided by CORBA implementations".

"The DDS standard culminates a persistent effort to ensure that a worldwide data distribution standard is freely available".

A requirement common to most real-time distributed applications is the need to pass data between different subsystem modules.

These modules may be on different processors or spread across multiple computers connected through a transport mechanism such as Ethernet, shared memory or a backplane such as VME.

These subsystems gather and generate data through interfaces with sensors, monitor and process data, or control and communicate with other subsystems.

Under the DDS standard, developers specify various QoS parameters such as rate of publication, rate of subscription and how long data are valid throughout the network.

Devices sending data become publishers and are only concerned with the specific data type they communicate.

Devices needing specific information are subscribers and only need to know about the particular data they wish to receive.

NDDS takes advantage of the capabilities inherent to the DCPS model to offer a high-quality implementation developed with the requirements of real-time and embedded systems in mind.

NDDS minimises the need for data copies resulting in increased performance.

Also, NDDS allows the application to pre-allocate resources, increasing reliability and real-time determinism.

"The DCPS communications model excels at efficiently distributing data between applications", states Gerardo Pardo-Castellote, Real-Time Innovations' Chief Technology Officer and co-author of the DDS specification.

"Establishing communications is simple".

"Publishers register data they will be producing with the middleware and subscribers register the data they are interested in receiving".

"The publisher just sends - or publishes - the data".

"This model is robust, efficient and data-centric".

"We are proud to offer the first commercial DDS implementation that meets the needs of many real-time systems".

NDDS has been shipped to selected customers and is immediately available in a limited-access version starting at US $46,920 for a three-user licence.

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