The Data Distribution Service (DDS) for real-time systems is an

Object Management Group The Object Management Group (OMG) is a computer industry standardization, standards consortium. OMG Task Forces develop enterprise integration standards for a range of technologies. Business activities The goal of the OMG was a common portabl ...

(OMG)

machine-to-machine Machine to machine (M2M) is direct communication between devices using any communications channel, including wired and wireless. Machine to machine communication can include industrial instrumentation, enabling a sensor or meter to communicate the ...

(sometimes called

middleware Middleware is a type of computer software that provides services to software applications beyond those available from the operating system. It can be described as "software glue". Middleware makes it easier for software developers to implement co ...

or connectivity framework) standard that aims to enable dependable, high-performance,

interoperable Interoperability is a characteristic of a product or system to work with other products or systems. While the term was initially defined for information technology or systems engineering services to allow for information exchange, a broader defi ...

real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...

scalable Scalability is the property of a system to handle a growing amount of work by adding resources to the system. In an economic context, a scalable business model implies that a company can increase sales given increased resources. For example, a ...

data exchange Data exchange is the process of taking data structured under a ''source'' schema and transforming it into a ''target'' schema, so that the target data is an accurate representation of the source data.A. Doan, A. Halevy, and Z. Ives.Principles of da ...

s using a

publish–subscribe pattern In software architecture, publish–subscribe is a messaging pattern where senders of messages, called publishers, do not program the messages to be sent directly to specific receivers, called subscribers, but instead categorize published me ...

. DDS addresses the needs of applications like aerospace and defense,

air-traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airs ...

autonomous vehicles Vehicular automation involves the use of mechatronics, artificial intelligence, and multi-agent systems to assist the operator of a vehicle (car, aircraft, watercraft, or otherwise).Hu, J.; Bhowmick, P.; Lanzon, A.,Group Coordinated Control o ...

, medical devices, robotics, power generation, simulation and testing,

smart grid A smart grid is an electrical grid which includes a variety of operation and energy measures including: *Advanced metering infrastructure (of which smart meters are a generic name for any utility side device even if it is more capable e.g. a f ...

management, transportation systems, and other applications that require real-time data exchange.

Architecture

Model

DDS is a networking

that simplifies complex network programming. It implements a

for sending and receiving data, events, and commands among the

node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines, ...

s. Nodes that produce information (publishers) create "topics" (e.g., temperature, location, pressure) and publish "samples". DDS delivers the samples to subscribers that declare an interest in that topic. DDS handles transfer chores: message addressing, data marshalling and de-marshalling (so subscribers can be on different platforms from 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 decoupled. Little design time needs be spent on handling their mutual interactions. In particular, the applications never need information about the other participating applications, including their existence or locations. DDS transparently handles message delivery without requiring intervention from the user applications, including: * determining who should receive the messages * where recipients are located * what happens if messages cannot be delivered DDS allows the user to specify

quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

(QoS) parameters to configure discovery and behavior mechanisms up-front. By exchanging messages anonymously, DDS simplifies distributed applications 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.

Interoperability

Both proprietary and

open-source software Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose. Op ...

implementations of DDS are available. These include

application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how t ...

s (APIs) and libraries of implementations in

Ada Ada may refer to: Places Africa * Ada Foah, a town in Ghana * Ada (Ghana parliament constituency) * Ada, Osun, a town in Nigeria Asia * Ada, Urmia, a village in West Azerbaijan Province, Iran * Ada, Karaman, a village in Karaman Province, ...

, C,

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

, C#,

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

Python Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...

, Scala,

Lua Lua or LUA may refer to: Science and technology * Lua (programming language) * Latvia University of Agriculture * Last universal ancestor, in evolution Ethnicity and language * Lua people, of Laos * Lawa people, of Thailand sometimes referred t ...

Pharo Pharo is an open source, cross-platform implementation of the classic Smalltalk-80 programming language and runtime. It's based on the OpenSmalltalk virtual machine called Cog (VM), which evaluates a dynamic, Reflective programming, reflectiv ...

and

Ruby A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sa ...

. DDS vendors participated in interoperability demonstrations at the OMG Spring technical meetings from 2009 to 2013.2011, March 2011, https://community.rti.com/content/presentation/omg-dds-interoperability-demo-20112012, March 2012, https://community.rti.com/content/presentation/omg-dds-interoperability-demo-20122013, March 2013, http://www.slideshare.net/GerardoPardo/dds-interoperability-demo-2013-washington-dc During demos, each vendor published and subscribed to each other's topics using a test suite called the shapes demo. For example, one vendor publishes information about a shape and the other vendors can subscribe to the topic and display the results on their own shapes display. Each vendor takes turns publishing the information and the other subscribe. Two things made the demos possible: the DDS-I or Real-Time Publish-Subscribe (RTPS) protocol, and the agreement to use a common model. Notional OMG DDS Interoperability

In March 2009, three vendors demonstrated interoperability between the individual, independent products that implemented the OMG Real-time Publish-Subscribe protocol version 2.1 from January 2009. The demonstration included the discovery of each other's publishers and subscribers on different OS Platforms (

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

and

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

) and supported

multicast In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...

and

unicast Unicast is data transmission from a single sender (red) to a single receiver (green). Other devices on the network (yellow) do not participate in the communication. In computer networking, unicast is a one-to-one transmission from one point in ...

network communications. The DDS interoperability demonstration used scenarios such as: * Basic connectivity to network using

Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP h ...

(IP) * Discovery of publishers and subscribers * Quality of service (QoS) Compatibility between requester and offerer * Delay-tolerant networking * Multiple topics and instances of topics * Exclusive ownerships of topics * Content filtering of topic data including time and geographic

History

Development of the DDS specification started in 2001. It was developed by Real-Time Innovations (RTI), a software framework company, and

Thales Group Thales Group () is a French multinational company that designs, develops and manufactures electrical systems as well as devices and equipment for the aerospace, defence, transportation and security sectors. The company is headquartered in Paris' ...

, a French defense company. In 2004, the

(OMG) published DDS version 1.0. Version 1.1 was published in December 2005, 1.2 in January 2007, and 1.4 in April 2015. DDS is covered by several US patents, among others. The DDS specification describes two levels of interfaces: * A lower data-centric publish-subscribe (DCPS) level that is targeted towards the efficient delivery of the proper information to the proper recipients. * An optional higher data local reconstruction layer (DLRL), which allows for a simple integration of DDS into the

application layer An application layer is an abstraction layer that specifies the shared communications protocols and Interface (computing), interface methods used by Host (network), hosts in a communications network. An ''application layer'' abstraction is speci ...

. Other related standards followed the initial core document. The Real-time Publish-Subscribe Wire Protocol DDS Interoperability Wire Protocol Specification ensured that information published on a topic using one vendor's DDS implementation is consumable by one or more subscribers using the same or different vendor's DDS implementations. Although the specification is targeted at the DDS community, its use is not limited. Versions 2.0 was published in April 2008, version 2.1 in November 2010, 2.2 in September 2014, and 2.3 in May 2019. DDS for Lightweight CCM (dds4ccm) offers an architectural pattern that separates the business logic from the non-functional properties. A 2012 extension added support for streams. A Java 5 Language PSM for DDS defined a Java 5 language binding, referred to as a Platform Specific Model (PSM) for DDS. It specified only the Data-Centric Publish-Subscribe (DCPS) portion of the DDS specification; Additionally, it encompasses the DDS APIs introduced by DDS-XTypes and DDS-CCM. DDS-PSM-Cxx defines the ISO/IEC C++ PSM language binding, referred to as a Platform Specific Model (PSM) for DDS. It provides a new C++ API for programming DDS that is more natural to a C++ programmer. The specification provides mappings for the

(API) specified in DDS-XTypes, and accessing

(QoS) profiles specified in DDS-CCM. Extensible and Dynamic Topic Types for DDS (DDS-XTypes) provided support for data-centric publish-subscribe communication where topics are defined with specific data structures. To be ''extensible'', DDS topics use data types defined before compile time and used throughout the DDS global data space. This model is desirable when static type checking is useful. A

Unified Modeling Language The Unified Modeling Language (UML) is a general-purpose, developmental modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system. The creation of UML was originally m ...

(UML) profile specified DDS domains and topics to be part of analysis and design modeling. This specification also defined how to publish and subscribe objects without first describing the types in another language, such as XML or OMG IDL. An

interface definition language interface description language or interface definition language (IDL), is a generic term for a language that lets a program or object written in one language communicate with another program written in an unknown language. IDLs describe an inter ...

(IDL) was specified in 2014 independently from the

Common Object Request Broker Architecture The Common Object Request Broker Architecture (CORBA) is a standard defined by the Object Management Group (OMG) designed to facilitate the communication of systems that are deployed on diverse platforms. CORBA enables collaboration between sys ...

(CORBA) specification chapter 3. This IDL 3.5 was compatible with the CORBA 3 specification, but extracted as its own specification allowing it to evolve independently from CORBA. Other protocols to be mentioned are: DDS-XRCE (DDS for eXtremely Resource Constrained Environments), this specification protocol allows the communication between devices of limited resources, like microcontroller for example and a DDS network. It makes publishing and subscribing to topics via an intermediate service in a DDS domain possible and DDS-RPC (RPC Over DDS) which defines Remote Procedure Calls. These provide a bidirectional request/reply communication and determine distributed services, and are detailed using a service interface. It also supports both synchronous and asynchronous method invocation. Starting with DDS version 1.4 in 2015, the optional DLRL layer was moved to a separate specification.

References

{{Ambient intelligence Computer standards Message-oriented middleware

Architecture

Model

Interoperability

History

See also

References