OPC UA Overview

Unified Architecture (UA) is the most recent OPC Specification of the OPC Foundation and differs tremendously from its predecessors. After 3 years of specification work and another year of prototyping the first version of Unified Architecture has been released end of 2006.

Prefacing facts:

• OPC UA is:
  service oriented, platform independent, scalable, extreme fast and secure
• OPC UA:
  does not require SOAP, is not a new version of XML DA, is not an enhancement of DA 3.0

Innovations

Although the original binding to COM/DCOM helped OPC to distribute well, however it also had some disadvantages:

• frequent configuration issues with DCOM
• no configurable timeouts
• only available for the Windows Operating System respectively COM
• only DCOM security, not Client specific
• requires opening of Firewall for DCOM

That and various other reasons lead to the decision to develop a new and independent communication stack for OPC UA which replaces COM/DCOM. The outstanding characteristics of this communication stack are:

• portable ANSI C implementation
• scalability from embedded controllers up to Mainframes
• stack can be compiled for multi-threaded as well as single-threaded/single-task operation, which is necessary for porting the stack onto embedded devices
• an own security implementation, based on latest standards
• configurable timeouts for each service
• chunking of large data packages

Additional features enhance the functionality. OPC UA combines todays Specifications (DA, AE, HDA, Commands, Complex Data) and simplifies common used functions like e.g. Browsing. In an Information Model now objects are provided these can e.g. contain data, but also can fire events or can provide historic data.