COVs and Subscriptions

SORIS supports subscribing to and unsubscribing from COVs and alarms.

A COV (Change of Value) is a type of WOT communication object that is used to notify all connected clients that the value of a specific property has changed. This method helps reduce web traffic by eliminating the need for clients to periodically send pull requests to obtain property values. When a COV is send to the SORIS Adapter, the adapter handles sending it out through a WebSocket connection only to the clients that are registered to receive COVs for the given property. The adapter provides a COV library and APIs to help create and send COVs.

Subscriptions allow clients to register for specific data over the WebSocket connection. Each client can create, update, and delete subscriptions by sending HTTP(S) requests. Subscriptions currently handle subscribing to alarms and COVs only. When setting up a subscription for alarms, the registered clients will either receive all alarms or no alarms. When setting up a subscription for COVs, the client will send a list of Things to subscribe to. The management station configures the subscription details required for communication through the WebSocket.