Dynamic Data Exchange (DDE) is a non-industrial specific predecessor to OPC.

Triconex DDE Server is a Windows application that enables DDE-compliant clients to request data from Triconex controllers. Under certain conditions, it also allows DDE clients to change data in a Triconex control program.

A DDE client can request data about input and output variables, memory variables, and system attributes  The client requests information about a Triconex controller from the DDE Server and the DDE Server then sends the requested information to the client.