Tuesday, December 4, 2007

OPC-HDA, what a bummer!

An integrator recently inquired about connecting FactorySQL to an OPC-HDA (historial data access) Server. A reasonable request. Hey, we're standardizing on OPC (DA) so why not? It seems reasonable that a historical data specification could bring some good to the table.

It turns out that OPC-HDA is another outdated COM based specification that was designed to standardize access to all of the different historian packages. Suppose you wanted a simple ActiveX graph or table back in the day. The idea is that it wouldn't have to know about the PLC. But wait, it still doesn't know how to poll the historical data. The user still needs to subscribe to tags, choose time ranges, etc. Sound like something that SQL's good at? Yeah, makes sense to use a standard interface. Plus, this many years later, all the vendors have jumped on the SQL bandwagon. And for good reason!

At this stage I can't even think of a practical way that FactorySQL could OPC-HDA that would make sense. Maybe if you needed to log from or write to an old HMI, but why? Logging works better from the PLC directly. Why would you ever need to write to an old HMI? It could only introducing unnecessary complexity and potential points of failure.

Aghh! Hurry, OPC-UA! We want web services! XML! Security models! NO MORE COM! Microsoft killed it so many years and major versions ago. Why can't industrial software follow suit!?!!? (I have my explanations, but will leave for another time)

4 comments:

Tom said...

We are actively working on putting the final touches on the OPC unified architecture which will give you significant functionality in terms of complex information modeling for historical data access. Couple that with the significant increase in reliability and security as part of the platform-independent unified architecture strategy and there will be no limit to what you can do in terms of the historical data access functionality. One of the key things in OPC unified architecture is support for legacy OPC COM-based products. Actually there are more historical data access products based on COM then you probably realized, and there are some pretty great reasons to use those products as we transition forward to the new service-oriented architecture of OPC UA.

Tom said...

We're also seeing a significant amount of development where vendors are rapidly deploying the OPC unified architecture and embedded devices including embedded HMI and of course your favorite PLC. This will allow exception-based processing and historical acquisition services to then be propagated up to visualization and logging applications as well as to the enterprise. Need I say more?

By the way my name is Thomas Burke and I am the president and executive director of the OPC Foundation. My vision is to make sure that the specifications in technology that the OPC Foundation deliverer are worth far more than the paper they are printed on.

We are actively soliciting vendors to participate in our early adopter program and to start beta testing many of the OPC Foundation deliverables including the rapper products that will allow existing legacy products to be easily transition and plug and play into the OPC unified architecture. Check out the OPC Foundation website for more information about this important program. This is not an advertisement this is a solicitation to make sure that we get as much feedback as possible as early as possible.

surferb said...

Tom - thanks for the feedback. I'm surprised you found my blog entry so quickly. I don't mind you advertising OPC. In fact, I appreciate you appearance here. I'm a strong proponent of standardization and, as far as I'm concerned, you guys are it! Expect cooperation from Inductive Automation as UA servers come up - any idea where Rockwell and Kepware are at there? I'll have to contact them.

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