Follow-up: OPC Versioning
Updated proxy/stubs available now
To recap, our article concluded with two main recommendations:
- OPC Foundation should re-issue all proxy/stub DLLs to include version resources, and
- all OPC vendors should install the latest proxy/stub DLLs, even where newer features are not being used.
The very good news is that OPC Foundation has pulled out all the stops to meet the first recommendation. This step now makes it simple for OPC vendors to ensure that their installation programs work well in multi-vendor scenarios.
To get the new proxy/stubs, and find out how and where they should be installed, visit the OPC Foundation's Downloads page.
Read on to find out how others in the OPC community perceived the problem.
Responses to the original article
Al Chisholm, OPC Technical Chair, was quick to reinforce our assessment of the problem, and of the way forward:
You are right on track. In fact I must confess that I had previously been chastised for failing to put a version in the Data Access 2 Proxy/Stub. It has been on my list of things to do for some time but never quite got to the top. This will finally motivate me to get it done soon!
Also, per your suggestion: I completely agree that both version 1 and version 2 vendors should (a) ship the version 2 proxy stub and (b) should install it per the discussion in the latest specifications (in the right directory with the right name and reference count). This minor change for version 1 vendors should be fairly easy to do even in the short term.
David Jenny, of Softing GmbH 4CONTROL, also agreed with the key points of the article, and stressed the importance of vendors updating their demo packages as well as their products:
Thank you for digging out this problem, it really has the potential to be a major knockout, mainly in multi-vendor scenarios, which definitely is an important design goal of OPC!
We strongly back your vote to deliver *ALL* OPC products (1.0 and 2.0) with the newer DA2.0 proxies and with the correct installation count setup to minimize the chance of end users corrupting their OPC installations. This patch of products should happen as soon as possible.
Vendors must not forget to also update all *DEMO* server/client packages, as they are most commonly installed for a quick try and deinstalled shortly after, which yields to the described mess again!
Our article suggested that OPC server vendors may need to update their installation programs, to come into line with OPC Foundation's guidelines on proxy/stub installation. Both Chris Doran and David Jenny pointed out our error of omission: OPC client vendors also frequently install the OPC proxies, and should likewise be implementing the Foundation's recommendations.
We should also have pointed out that the Alarms and Events proxy already has a version resource.