I just have just one word for OPC-Xi ... Why? Okay, I get it, it has taken forever to get the OPC-UA show on the road. And yes, Xi is a quick and dirty solution to get around classic OPC which is based on DCOM. But it's a short-term solution in a field that demands longer-term solutions.Forget the fact that Xi, like classic OPC, is vendor specific (depends on Microsoft technology). The bigger point is how many standards do we need? It's already to the point of madness. Isn't that the point of OPC standardization?
OPC-UA is now an accomplished fact. We recently attended the OPC-Interop conference in Nuremberg, Germany and were pleased with the heavy attendance. In fact, we successfully tested Ignition OPC-UA against nine other UA servers and ten other UA clients. Commercial products are now available from a large and ever growing number of vendors.
The more telling point is that OPC-Xi has no validation testing available (to my knowledge). And there are no interop conferences to ensure compatibility (also to my knowledge - correct me if I'm wrong). So is there really interoperability? I don't know. Take your chances.
NEWS FLASH – OPC-Xi is DEAD! Actually, it has been renamed to OPC .NET 3.0 (WCF Edition). Man, that is a mouthful to pronounce. As I was writing this one of our developers pointed out this recent change to me. By the way, WCF is the new Microsoft replacement for DCOM.
2 comments:
The best info I can find on Xi is available at: http://expressinterface.com/
It appears that Emmerson supports it, Advosol has OPC-Xi to DA wrappers, and Indusoft has incorporated Xi client support within their HMI package.
I feel less embarrassed at not remembering OPC-Xi at first mention. While UA (correctly) gains momentum in the spotlight, Xi is best left as a UA contingency that was never necessary. I don't think many industrial professionals have heard of the standard - or are missing anything.
I completely agree. OPC .NET 3.0 (WCF Edition) seems like dead end technology. Besides being Microsoft specific, it lacks many required features. For example, support for a complex address space is missing. This means it is hard to develop complementary standards over it like PLCOpen and ADI have done. Without the complementary standards you are not really furthering interoperability.
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