OPC and XML/SOAP
- OPC XML-DA Specification
- XML-DA Toolkits
- XML-DA Software
- Public XML-DA Servers
- Proprietary Applications of XML and OPC
XML and SOAP Resources
- XML - the Extensible Markup Language
- SOAP - the Simple Object Access Protocol
- XML and SOAP for Delphi Developers (link to our Delphi page)
OPC and XML/SOAP
OPC XML-DA Specification
OPC Foundation's intention to make use of XML was first announced at a press conference during 1999 ISA. The original press release is still available.
After a gestation period of almost four years, the OPC XML-DA 1.00 specification was finally released in July 2003. Version 1.01, with minor clarifications, was released December 2004. It may be may be downloaded via OPC Foundation's Downloads page.
These documents provide background information about OPC XML-DA and SOAP:
- XML-DA opens windows beyond the firewall by Frank Iwanitz of Softing, published in the Industrial Ethernet Book.
- OPC brings XML-DA to the factory floor by Jim Luth of ICONICS.
- Comparison of the OPC DA and XML-DA specifications by Advosol Inc.
XML and SOAP also form cornerstones of Microsoft's .NET strategy. Microsoft's TechNet pages have a useful feature on Microsoft .NET for Manufacturing, which specifically addresses OPC.
OPC XML-DA toolkits are available from vendors including Advosol, ICONICS, Kassl, Softing and Technosoftware. See our Toolkits page for more information.
OPC Foundation members may obtain XML-DA sample code (including source) from the Foundation's Downloads page. These samples are reliant on Microsoft's .NET framework, and are produced to a very high standard.
Advosol has made available a number of free trial downloads.
- XML-DA Server Side Gateway
- XML-DA Server Side Gateway is an XML-DA server with an integrated DA client. It allows any OPC Data Access (COM) server to be made available to XML-DA clients. Includes a variety of useful XML-DA client samples, plus a new configuration diagnostic utility.
- XML-DA Client Side Gateway
- XML-DA Client Side Gateway is a proxy, allowing OPC DA (COM) clients to access XML-DA web services.
- XML-DA Sample Clients
- Bundle of clients made available by Advosol to allow users to experiment further with OPC XML-DA. Now includes additional ASP, ASP.NET, and HTML samples. See also Advosol's article at The Code Project.
- OPC Historian Web Service
- Not strictly an XML-DA product, Advosol's OPC Historian Web Service acts as a web service gateway to HDA servers. Any HDA server may be exposed as a .NET web service, allowing archived data to be accessed from any location.
Advosol has updated its client-side and server-side XML-DA Gateways and the XMLDA.NET Client Component with security support based on Microsoft WSE 3.0. Advosol says this allows remote XML-DA and (COM) DA servers to be accessed using the same type of security as will be provided in OPC UA.
See also our Source/Toolkits page for information on XML-DA toolkits by Advosol.
See our Source/Toolkits page for information on XML-DA toolkits by ICONICS.
Kassl GmbH publishes the excellent dOPC range of products, consisting of:
- dOPC XGate
- Allows any DA COM server to be accessed by XML-DA clients. New version 2.05 passes the OPC Foundation Compliance Test and includes numerous enhancements. These include support for automatic reconnection to the underlying server, better performance, full request/response logging, and improved DA 3 support.
- dOPC XCOM
- Allows DA COM clients to access XML-DA servers.
- dOPC Explorer
- A general purpose DA client, capable of accessing both COM and XML-DA servers; includes simple trend charts, and is free for non-commercial use. Now supports DA 3 and XML-DA 1.01.
See also our Delphi page for information on Kassl's dOPC Toolkits with XML-DA support.
Each of Kassl's products is compatible with Windows versions from Windows 98 onwards, and there are no dependencies on either .NET or pre-installed web servers. dOPC XGate, for example, includes its own integrated web server.
PyOPC is an Open Source framework for rapidly creating XML-DA clients and servers using the Python language.
As well as the actual Python language, PyOPC is dependent on the Zolera SOAP Infrastructure for SOAP message handling, and the Twisted server framework for server functionality.
The PyOPC download includes sample XML-DA client and server implementations.
See our Source/Toolkits page for information on XML-DA toolkits by Softing.
See our Source/Toolkits page for information on XML-DA toolkits by Technosoftware.
Public XML-DA Servers
A number of XML-DA servers have been made available for general use. Each of these systems may be reached directly via the Internet.
Advosol Inc. operates XML-DA servers, including:
- The XML-DA Gateway interfaces to a (COM) DA server.
- The XML-DA Rapid Server Toolkit provides a native XML-DA sample server.
- OPC Foundation
- OPC Foundation operates an XML-DA server, running sample code available to Foundation members. Connection information is supplied with the same sample code. This server runs Microsoft Windows 2000 and IIS 5.0.
Proprietary Applications of XML and OPC
IOServer's OPC server product includes an XML server capability as standard (follow the link to 'XML Server interface'). This is essentially an HTTP server, using a non-standard port number, which serves a proprietary protocol consisting of XML request and response packets. The protocol offers a subset of the functionality of OPC Data Access, but is very different from the OPC Foundation's draft XML specification.
IOServer is available as an evaluation download, and there is also a sample web page, using the Vector Markup Language (VML), which acts as a client to the XML server.
XML and SOAP Resources
The World Wide Web Consortium is the body responsible for XML-related standards: see their XML page.
Microsoft's MSDN Online has a useful XML Developer Center. XML.ORG maintains a catalog of published XML schemas and vocabularies, while Cafe con Leche is good for XML news.
The SOAP 1.1 specification may be accessed at www.w3.org/TR/soap/. SOAP 1.1 is supported by most current implementations, but SOAP 1.2 is also now a W3C Recommendation.
You should also take a look at Microsoft's Web Services Developer Center on MSDN. Among other useful links, you'll find here information about Microsoft's SOAP Toolkit. This free download allows Visual Studio 6.0 (or later) developers to begin SOAP development right away. Version 3.0 of this toolkit is the most recent release.
One of SOAP's chief architects was Microsoft's Don Box, formerly of DevelopMentor. Don wrote an early SOAP article for MSDN: A Young Person's Guide to The Simple Object Access Protocol.
MSDN also has Simply SOAP, by Roger Wolter, a Program Manager for SOAP at Microsoft.
Cetus Links has a page dedicated to SOAP.