OPC Data Exchange (OPC-DX) is a standard that builds upon the existing OPC Data Access (OPC-DA) standard. OPC-DA provides interfaces that allow for the transfer of data between an OPC-DA server and an OPC-DA client. Typically, OPC-DA clients subscribe to one or more OPC-DA servers to acquire data, and OPC-DA servers provide data to one or more OPC-DA clients. Over time and with the large acceptance of OPC-DA by the market, end-users demanded the ability not only to share data between clients and servers, but to share data between one or more servers.