Connectivity Framework
4 : Connectivity Framework Layer
meaningful data . Explicit data typing allows intelligent or standard technologies that can map data representations .
4.1.4 DATA RESOURCE LIFECYCLE ( CRUD )
A connectivity framework should provide a means to manage the lifecycle of a data object . These include the following four critical operations , abbreviated as “ CRUD ”:
• create ( C ): a means of creating or introducing a new data object ,
• read ( R ): a means of observing the state of a data object ,
• update ( U ): a means of updating the state of a data object and
• delete ( D ): a means of deleting a data object .
4.1.5 STATE MANAGEMENT
IIoT components need access to high frequency , high-volume data beyond when it was initially produced . For example , a component may require the last n updates to plan the next action or make a prediction .
A connectivity frameworks can manage the historical state of the data objects . They can cache the last n updates to a data object so that applications can simply examine the historical state .
Connectivity frameworks can get the current state , even though the state may have changed long before a participant joined the system or reconnected . It may maintain a virtual view of the data objects associated with an endpoint and synchronize it when a connection is re-established .
4.1.6 PUBLISH-SUBSCRIBE
A connectivity framework should support the publish-subscribe data-exchange pattern in which a component publishes data on a well-known topic without regard to subscribers , and a component subscribes to data from the well-known topic without regards to publishers . This decouples publishers from subscribers , using only the channel for the topic at hand , so that components are loosely coupled and can be replaced independently of one another . An endpoint may operate in both a publisher and subscriber role . This data exchange pattern is also called the push data-exchange pattern .
The publish-subscribe data exchange pattern is useful for one-to-many and many-to-many data distribution scenarios , including streaming , alarms and events , command and control , and configuration ( Industrial Internet Reference Architecture , IIRA ) 1 .
The decoupling in space ( location ) and time ( asynchronous delivery ) provided by publishsubscribe data exchange pattern achieves the reliability , performance and scale demanded by IIoT systems . It also decreases the likelihood of fault propagation and simplifies incremental updating and evolution .
1
See [ IIC-IIRA2015 ] IIC : PUB : G5 : V1.0 : PB : 20170228 - 29 -