OPC Data eXchange (OPC DX) Specification

OPC Data eXchange (OPC DX) is a specification that defines how OPC servers exchange data with other OPC servers. While a small number of vendors incorporated this specification in their products, there are no commercial implementations of this technology. Instead, corporations are using various forms for OPC bridging products that transfer data between OPC Servers.

The OPC Foundation is responsible for defining and maintaining the OPC DX specification. The have defined interfaces to OPC Data Access Servers, Alarm and Event Servers, Batch Servers, and Historical Data Access Servers. These servers acquire data from the plant floor and move it vertically into the enterprise system.

In contrast, OPC Data eXchange (OPC DX) has been designed to move plant floor data horizontally between OPC DA servers. By presenting this new technology, the OPC DX enables data interoperability between OPC based systems (including DCOM and XML based systems running over Ethernet) including PLCs, HMI/SCADA, Devices, and PCs.

The purpose of this specification is to continue OPC’s goal of enabling and promoting interoperability of applications.

OPC DX does not specify a new method for data transfers. Instead, it relies on OPC Data Access (OPC DA) data transfer capabilities already in use today. This specification defines the behavior of the OPC DX server as it relates to control and monitoring the data transfer from DA servers to itself.

This specification is intended for developers of OPC compliant DX Clients and Servers. It is assumed that the reader is familiar with Microsoft COM, Web Services, XML, and SOAP. It is also recommended that the reader review the reference documents described in Section 1.5.

OPC DX, in contrast to OPC DA, is used primarily for horizontal data flows between OPC servers. OPC DX is designed to provide for the direct transfer of data from one or more OPC DA and DX servers to an OPC DX server, without the need for intermediate clients or servers to access the data from one server and forward it to another.

To support these capabilities, OPC DX has the following goals:

• Exchange data between OPC DA servers in environments containing multiple bus technologies.
• Define a standard interface for OPC DX server configuration.
• Use OPC DA where practical.
• Provide an easy migration path for existing OPC DA vendors.
• Insulate the design from communication technologies, while maintaining interoperability within as many products as possible.

Visit the OPC Foundation website to download the OPC Data eXchange (OPC DX) specification.