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-