The OPC Foundation provides specifications for data exchange in industrial automation.
There is a long history of COM/DCOM-based specifications, most prominent
OPC Data Access (DA), OPC Alarms and Events (A&E), and OPC Historical
Data Access (HDA), which are widely accepted in the industry and implemented
by almost every system targeting industrial automation.
Now the OPC Foundation has released a new generation of OPC specifications
called OPC Unified Architecture (OPC UA). With OPC UA, the OPC Foundation
fulfills a technology shift from the retiring COM/DCOM technology to a serviceoriented
architecture providing data in a platform-independent manner via Web
Services or its own optimized TCP-based protocol. OPC UA unifies the previous
specifications into one single address space capable of dealing with current data,
alarms and events and the history of current data as well as the event history. A
remarkable enhancement of OPC UA is the Address Space Model by which vendors
can expose a rich and extensible information model using object-oriented
techniques. OPC UA scales well from intelligent devices, controllers, DCS, and
SCADA systems up to MES and ERP systems. It also scales well in its ability to
provide information; on the lower end, a model similar to Classic OPC can be
used, providing only base information, while at the upper end, highly sophisticated
models can be described, providing a large amount of metadata including complex
type hierarchies.