In a “set” operation, a requestor can set the value of a writeable interface property for a provider. Set operations can be initiated by the requestor as a synchronous operation using the DOFObject.set method, or as an asynchronous operation using DOFObject.beginSet.

In an “invoke” operation, a requestor calls an interface method, and the provider executes it and returns results (if the method has return values). Invoke operations can be initiated by the requestor as a synchronous operation using the DOFObject.invoke method, or as an asynchronous operation using DOFObject.beginInvoke.

• To discover whether the provider of an interface is currently running and connected to the network
• To enable a requestor to discover multiple providers of an interface
• To support other operations that require interest
• To cause a provider that is capable of providing an interface to begin providing it on demand
• To cause datagram connections between a requestor and provider to be upgraded to streaming connections to support operations that need a streaming connection
• To reduce network traffic by mapping a direct route between a requestor that is “interested” in a binding and a provider that provides it

Activate-level interest is a request to begin providing an interface. A provider can be programmed to begin dynamically providin​g an interface in response to activate-level interest.

A “query” operation is used by a requestor to parse the “provides” that it receives in response to an “interest” operation. A query operation will not search the network for providers. It will only find “provide” operations that the requestor is storing in state on its local system. It’s important to note that because the system will not store provide operations without a matching interest operation, queries are useful only in conjunction with interest.