Here is a post with links to all the OPC DA 3.0 specification overview.   Thanks Dale for the link up, and the good suggestion for this post

OPC DA 3.0 Specification Overview

Part I - Introduction and Overview
Part II - General Information
Part III - OPC Server object
Part IV - OPC Group object (Overview, Item/Group management)
Part V  - OPC Group object continued (Read/Write methods)
Part VI - Client side interfaces and Installation issues.

I hope everyone gets as much from reading it, as I did from writing it.

Actually, after following ‘polyphasic’ mention in Gary Mintchell’s sleep survey, I realized how useful it is to end multi stage posts with link backs to all the preceding ones.  Live and learn.  If you can’t sleep some night, check out the posting on polyphasic sleep.  I can think of several dozen things I could get done with an extra 30-40 hours a week, even if it is in the middle of the night.  Just imagine the OPC products you could dream up.