OPC Unified Architecture
OPC Unified Architecture (UA) is the OPC Foundation's next generation technology for secure, reliable, and interoperable transport of raw data and preprocessed information from the shop floor into production planning or the ERP system. Softing AG has established a migration strategy allowing OPC manufacturers to migrate easily to the new OPC architecture. As a member of the UA Eary Adopter Group of the OPC Foundation, Softing actively contributes to the launch of the new technology generation.
With OPC UA the OPC Foundation realizes its vision of "global" interoperability, i.e. of making possible a standardized data exchange between software applications independently of the manufacturer they come from, the programming language they were developed in, the operating system they run on or the place they are located at.
New Applications Using OPC UA
OPC has up to now, with the exception of the OPC XML-DA specification, made use of the Microsoft Distributed Component Object Model (DCOM), which is part of the Windows operating system. The nearly "ubiquitous" Microsoft platform, even in industrial environments, is certainly one reason for the rapid distribution of OPC. However DCOM restricts the use of OPC technology to Windows operating systems. For years now, industry has been calling on the OPC Foundation to provide an OPC standard that can be utilized on different operating systems (manufacturers of ERP systems on Unix platforms and manufacturers of embedded systems with real-time operating systems such as VxWorks, QNX, etc).
OPC UA is no longer based on DCOM but on a service oriented architecture (SOA). The OPC UA kernel is composed of a set of UA services, which form an interoperability framework.
Interoperability FrameworkThis framework forms an autonomous entity with a defined interface to the underlying proprietary technology. In this context OPC UA is more or less independent of the technology upon which the operating system is based and is easy to port. The OPC Foundation provides a C, Java, and .NET SDK (Software Development Kit) for use when porting to different platforms.
The range of services, size, performance, and platforms supported by UA servers can be modified and scaled. The server properties are specified in a profile and can be queried by the client. Exceptionally lean UA servers with only a small set of UA services, e.g. just Data Access and minimal security, can be implemented for embedded systems with limited memory. On the other hand, memory resources are not particularly relevant for a server computer in the IT department, which means that UA servers can be very powerful and expanded to full functional capability.
Unification Leads to Simplification
The market requires the OPC foundation to provide better integration of alarms in the address space of a Data Access Server, especially for the process industry and building automation. To date three different OPC servers - DA, AE, and HDA - with different semantics have been required, for example to capture the current value of a temperature sensor, an event resulting from a temperature threshold violation, and the historic mean temperature.
OPC UA enables all three types of data to be accessed by a single OPC server. As a result UA unifies the current DA, AE, HDA models and additional program calls into a single integrated address space. This unified architecture reduces the number of OPC components to be installed and simplifies configuration and installation. UA also provides the additional option of storing a more detailed description of a data point directly in the OPC UA object, e.g. unit, scale factor etc. In this way OPC UA makes data management simpler, more centralized, and richer in additional information.
Softing has already established a migration strategy allowing OPC manufacturers to migrate easily to the new OPC architecture.