DDS™ - The Proven Data Connectivity Standard for IoT™ Nov. 2016 | Page 5

QoS DATA QoS READER DATA WRITER DATA WRITER DATA WRITER DATA WRITER QoS QoS TOPIC A QoS QoS DATA READER QoS DATA READER QoS TOPIC C QoS QoS QoS DDS DOMAIN QoS DATA WRITER TOPIC B FILTERS TOPIC D FILTERS DATA QoS READER QoS DATA READER QoS DATA READER DDS provides QoS-controlled data-sharing. Applications communicate by publishing and subscribing to Topics identified by their Topic name. Subscriptions can specify time and content filters and get only a subset of the data being published on the Topic. Different DDS Domains are completely independent from each other. There is no data-sharing across DDS domains. GLOBAL DATA SPACE DDS conceptually sees a local store of data called the “global data space.” To the application, the global data space looks like native memory accessed via an API. You write to what looks like your local storage. In reality, DDS sends messages to update the appropriate stores on remote nodes. You read from what looks like a local store. Source WPT1 WPT2 WPTN Speed Power Phase 37.4 10.7 50.2 122.0 74.0 150.07 -12.20 -12.23 -11.98 Inside a DDS domain the unit of information sharing is data-objects within Topics. The topic is identified by its name and the data-object by some ‘Key” attributes. This is similar to how key attributes are used to identify records in a Database. This figure is conceptual. DDS communicates peer-to-peer and does not require the data to be brokered by a server or cloud. 5 WHAT IS DDS? The essence of data centricity is that DDS knows what data it stores and controls how to share that data. Programmers using traditional message-centric middleware must write code that sends messages. Programmers using data-centric middleware write code that specifies how and when to share data and then directly share data values. Rather than managing all this complexity in the application code, DDS directly implements controlled, managed, secure data sharing for you.