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OPC and XML in Building Automation

LOYTEC, an Austrian manufacturer of building automation products, embeds the OPC XML/DA standard into one of its building automation products using an OPC C++ Toolkit from Softing.

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In 2003, an open letter to the Building Controls industry proposed to establish a consortium that would work on the creation of a guideline for use of eXtensible Mark-up Language (XML) and Web Services in building automation and control applications. The first paragraph of the open letter reads:

“The Building Controls industry has made great strides over the last 10 years in the creation of communications standards. Both BACnet and LonTalk are now viable, commercially accepted solutions that provide owners with open communications. Yet while we have made great progress in these areas as an industry, there has been an emergence of a larger, more globally accepted standard created by the world of Information Technology. In particular the broad acceptance and ever lowering cost of Ethernet/TCP/IP/ XML communications is finding its way into our industry.”

In building automation today, it is frequently necessary to provide access to data points in a building via conventional Web-based methods. This may be required for operating controls in Web browsers, for connections to standard software packages for visualization, or for facility management. Direct access from Enterprise Resource Planning (ERP) systems to building data is becoming increasingly important as well. OPC XML/DA (Data Access) provides for a standardized, vendor-neutral Web service that can also be used in building automation.

Conventional Distributed Component Object Model (DCOM) solutions are usually based on a central OPC server. The disadvantage of this is that it calls for a dedicated Windows personal computer and represents a single point of failure.

The L-OPC from LOYTEC, an Austrian manufacturer of building automation products, is the first embedded OPC Server according to the OPC XML/DA standard. The L-OPC implements access to a user-defined set of data objects through the use of Web services according to the OPC XML/DA standard. No dedicated PC is necessary. By using Web services, the data access is very firewall friendly and the L-OPC seamlessly integrates into systems connected via the Intranet/Internet. In addition, the L-OPC can serve customized Web pages to display network data. With JavaScript or Java applets, the L-OPC can also display active content on its Web pages.

By mapping native data points to Web services, several L-OPCs can be combined to form a type of distributed Web services gateway. The L-OPC also distributes OPC network traffic to the respective local segments. LOYTEC selected the OPC C++ XML-DA Toolkit from Softing, based near Munich, Germany, for implementing its OPC Server because it enables the LOYTEC design team to concentrate on the project goal and not on learning the intricacies of DCOM, SOAP, or other underlying Microsoft technologies. The porting of Softing’s C++ XML-DA Toolkit from the Windows platform to the embedded operating system platform was easily accomplished due to Softing’s strict adherence to the ANSI C++ standard while writing source code. In the device, native data points are exported from EIA-709 (Lon networks) or BACnet to OPC-tags.
Integration with standard OPC DA Client applications (e.g. supervisory control and data acquisition—SCADA systems) is easily performed with Softing’s OPC Easy Connect Suite, a comprehensive set of OPC middleware products designed to simplify the configuration and to optimize the operation of OPC Client and Server systems. Softing’s OPC Bridge, one component of the Easy Connect Suite, serves as an “OPC gateway” used to seamlessly bridge between OPC Specifications, for example, between OPC DA and OPC XML-DA or between OPC DA V1.0 and OPC DA V3.0. In addition, the OPC Bridge has been used to achieve full OPC compliance for outdated OPC Servers, such as OPC Servers that adhere only to the OPC DA V1.0 specification.

The embedded OPC server of the L-OPC is able to manage up to 1,000 OPC tags per device and is ideally suited for the following applications:
•Interface for visualizations and SCADA systems
•Web visualization of individual areas
•Room control via a Web browser 

In addition to the OPC XML-DA technology the LOYTEC L-OPC supports data recording, monitoring of alarm states, and scheduling of daily routines.

Dr. Stefan Soucek of LOYTEC summarizes the company’s experiences during the development. “We reviewed several options for developing an embedded OPC server. Softing’s XML-DA Toolkit proved to be very easy to use and quickly portable. The quality of the OPC software and the support confirmed that our decision to opt for Softing as our partner was perfect.”

The OPC standard as a widely accepted industry standard for visualization applications ensures a high level of interoperability.

Softing, a member of the European Steering Committee of the OPC Foundation and author of the OPC Book, actively contributes to the success of OPC by providing high quality OPC products that enable its customers to stay in the lead.

To read the full letter to the Building Controls industry, click here. (

For more information on how Softing can assist you, please visit

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