The OPC Foundation has announced the release of its OPC XML Data Access (XML DA) specification, as part of a move towards platform-independent interoperability and generic support for Internet-based Web Services.
The new specification provides the gateway to the Internet for OPC data and OPC information to be transferred to and from any OPC-enabled device. A ‘wrapper’ is being provided as an easy migration path for the estimated 3000+ OPC DA products in use today.
The OPC XML data access specification enables vendors to add OPC support to any device on the factory floor that is capable of supporting a Web service. This facilitates the OPC data exchange protocol for communicating data and information seamlessly and transparently between devices independent of the operating system and networking technology that the specific device employs.
OPC Foundation President Tom Burke said: ‘Our vision is to ensure members can build integrated and interoperable systems. Internet-based HMI is one possibility opened up by OPC XML DA. Others include web-enabled field devices and enterprise-wide management systems. The OPC XML Data Access specification is now available complete with sample code for immediate implementation.’
Prior to the OPC XML data access specification, OPC required the use of Microsoft COM/DCOM to provide data access and exchange services between multiple vendor products. However, DCOM cannot pass firewalls so communications over the Internet have previously been impossible.
XML (eXtensible Markup Language) is one of the key enabling technologies worldwide for achieving global interconnectivity and it has industry-wide support as a standardized way of handling data among systems using a variety of operating systems. Since it is text-based, XML can pass through firewalls.
The OPC XML DA specification defines how XML is used by OPC clients and OPC servers, allowing end-users to deploy systems with commercial off-the-shelf products for true interoperability without having the restrictions of local networks.
Definitions for supporting Web Services are also provided, enabling users to make simple application-to-application connections over the Internet.