Why OPC-UA?

There is several reason to choose a new architecture, the biggest one, in my opinion being getting rid  of the COM architecture, which Microsoft deemphasizes in favor of cross platform, and the other being platform independent and service orientated (The mantra being Service Orientate or die). Yes with OPC-UA you no longer need Windows, it will run on you MAC, your Linux or of course Windows. It will connect across the internet and doing so in a much safer way than any other Automation protocol. It will do it using common public and private key technology.

There are several sites on the net, explaining about this. The OPC foundation has a lot of information, but there are other sites, which explains this

Here are some links worth looking at:

commsvr.com

OPC Foundation