Data Distribution Service: Difference between revisions

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{{Short description|Object Management Group standard}}

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The '''Data Distribution Service''' ('''DDS''') for real-time systems is an [[Object Management Group]] (OMG) [[machine-to-machine]] (sometimes called [[middleware]] or connectivity framework) standard that aims to enable [[Safety-critical|dependable]], [[Many-task computing|high-performance]], [[interoperable]], [[Real-time computing|real-time]], [[Scalability|scalable]] [[data exchange]]s using a [[publish–subscribe pattern]].

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DDS allows the user to specify [[quality of service]] (QoS) parameters to configure discovery and behavior mechanisms up-front. By exchanging messages anonymously, DDS simplifies distributed applications and encourages modular, well-structured programs. {{citation needed|date=October 2019}}

DDS also automatically handles hot-swapping redundant publishers if the primary fails. {{citation needed|date=October 2019}} Subscribers always get the sample with the highest priority whose data is still valid (that is, whose publisher-specified validity period has not expired){{citation needed|date=January 2024}}. It automatically switches back to the primary when it recovers, too{{citation needed|date=January 2024}}.

=== Interoperability ===

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== History ==

Development of the DDS specification started in 2001. It was developed by Real-Time Innovations (RTI), a software framework company, and [[Thales Group]], a French defense company. In 2004, the [[Object Management Group]] (OMG) published DDS version 1.0.<ref>{{Cite web |title= Data Distribution Service (DDS), Version 1.0 |date= December 2, 2004 |publisher= Object Management Group |url= http://www.omg.org/spec/DDS/1.0 |access-date= November 9, 2016 }}</ref> Version 1.1 was published in December 2005,<ref>{{Cite web |title= Data Distribution Service (DDS), Version 1.1 |date= December 4, 2005 |url= http://www.omg.org/spec/DDS/1.1 |access-date= November 9, 2016 }}</ref> 1.2 in January 2007,<ref>{{Cite web |title= Data Distribution Service (DDS), Version 1.2 |date= January 1, 2007 |url= http://www.omg.org/spec/DDS/1.2 |access-date= November 9, 2016 }}</ref> and 1.4 in April 2015.<ref>{{Cite web |title= Data Distribution Service (DDS), Version 1.4 |date= April 10, 2015 |url= http://www.omg.org/spec/DDS/1.4 |access-date= November 9, 2016 }}</ref>

DDS is covered by several US patents,<ref>[https://wwwpatents.google.com/patentspatent/US8874686 US Patent US8874686]</ref><ref>[httphttps://wwwpatents.google.com/patentspatent/US8671135 US Patent US8671135]</ref><ref>[httphttps://wwwpatents.google.com/patentspatent/US8150988 US Patent US8150988]</ref><ref>[httphttps://wwwpatents.google.com/patentspatent/US9015672 US Patent US9015672]</ref> among others.

The DDS specification describes two levels of interfaces:

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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.<ref>Extensible and Dynamic Topic Types for DDS (DDS-XTypes), 1.0, formal/2012-11-10, November 2012, http://www.omg.org/spec/DDS-XTypes/1.0/PDF</ref>

A [[Unified Modeling Language]] (UML) profile specified DDS domains and topics to be part of analysis and design modeling.<ref>UML Profile for Data Distribution, version: 1.0, http://www.omg.org/cgi-bin/doc?ptc/10-05-17.pdf </ref> This specification also defined how to publish and subscribe objects without first describing the types in another language, such as XML or OMG IDL.<ref>DDS-Java: Java 5 Language PSM for DDSVersion 1.0, ptc/2012-12-01, March 2013 http://www.omg.org/spec/DDS-Java/1.0/Beta3/PDF</ref>

An [[interface definition language]] (IDL) was specified in 2014 independently from the [[Common Object Request Broker Architecture]] (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.<ref>{{Cite web |title= Interface Definition Language (IDL), Version 3.5 |date= March 1, 2014 |publisher= OMG |url= http://www.omg.org/spec/IDL35/3.5/ |access-date= November 9, 2016 |archive-url= https://web.archive.org/web/20170121033326/http://www.omg.org/spec/IDL35/3.5/ |archive-date= January 21, 2017 |url-status= dead }}</ref>

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 <ref>{{Cite web|title=About the DDS For Extremely Resource Constrained Environments Specification Version 1.0|url=https://www.omg.org/spec/DDS-XRCE|access-date=2021-03-12|website=www.omg.org}}</ref> 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. <ref>{{Cite web|title=About the RPC Over DDS Specification Version 1.0|url=https://www.omg.org/spec/DDS-RPC/1.0|access-date=2021-03-12|website=www.omg.org}}</ref>

Starting with DDS version 1.4 in 2015, the optional DLRL layer was moved to a separate specification.<ref>{{Cite web |title= DDS Data Local Reconstruction Layer (DDS-DLRL) |date= April 2015 |url= http://www.omg.org/spec/DDS-DLRL/ |access-date= November 9, 2016 }}</ref>

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== References ==

{{Reflist|30em}}

{{Ambient intelligence}}