**Interoperability Testing is a process where OPC
vendors attend an event hosted by the OPC Foundation
and test their products with the products supplied by
other OPC vendors. These events are called Interoperability
(IOP) Workshops and occur three times a year (once in
Europe, the US and Japan).
The interoperability test process requires that OPC
vendors run a series of standard tests for each combination
of a OPC Client and an OPC Server product. The results
of the these tests are collected and displayed
in the product catalogue.
OPC Users should look for OPC Client and OPC Server
products that have been tested with several products
from other OPC vendors for each of the specifications
that the products support.