What is OPC Unified Architecture (OPC UA)?
OPC Unified Architecture (UA) is a platform-independent, service-oriented protocol design that integrates all the functionality of the individual OPC Classic specifications into one extensible specification framework. This approach accomplishes functional equivalence to OPC Classic, with all COM OPC Classic specifications mapped to UA. It also achieves platform independence with support for ARM/x86, Windows/non-Windows, and security, including encryption, signing, and authentication. Extensibility, the ability to add new features without affecting existing applications, and information modeling, which creates standard and custom information structures from unstructured data, are also key components of OPC UA.
OPC Classic vs. OPC UA
OPC UA provides a single, secure, and reliable cross-platform framework for accessing a variety of data. In OPC “Classic,” each protocol is its own standard with no relation to or compatibility with one another. Services (read, write, etc.) unique to each protocol are used to access unique data within each model. With OPC UA, services are abstracted from the information models they can access. Client applications programmed to be aware of the information model they want to access can use a common set of services to obtain the data.
History of OPC UA
First released in the mid-1990s, the original OPC standard abstracted PLC-specific protocols (such as Modbus, DeviceNet, etc.) into a common API allowing HMI/SCADA systems to interface with “middleware” that would convert generic OPC read/write requests into device-specific requests. The technology took hold, and an entire industry of products emerged that allowed systems to be implemented using best-of-breed products seamlessly interfacing via OPC. First iterations of the OPC standard were restricted to Windows operating systems, and thus the acronym OPC was derived from “OLE (object linking and embedding) for Process Control.” The OPC Classic specifications, as they are now known, have been widely adopted across multiple industries. As manufacturing systems and organizations evolved, industries faced new challenges, including security and data contextualization. The OPC Foundation developed OPC UA to address these needs and to provide a feature-rich, extensible platform that was scalable and future-proof.
Benefits of OPC Unified Architecture
OPC UA was designed to enhance and surpass the benefits of OPC Classic. Though functionally equivalent to OPC Classic, OPC UA is capable of far more.
Platform Independence
OPC UA supports a large range of Windows and non-Windows systems, from devices as small as embedded microcontrollers to large, cloud-based server infrastructure.
Security
OPC UA offers robust security options like user authentication and access controls, as well as the use of industry-standard Transport Layer Security (TLS) for message signing and message encryption.
Functional Equivalence
Just like OPC Classic, OPC UA offers helpful features to speed integrations like OPC server discovery, address space browsing, and data change subscriptions. OPC UA also supports on-demand, procedural commands like explicit reads and writes often critical for process control.
OPC UA specifications
The OPC UA specification offers functionally equivalent features to the individual OPC Classic specifications, as well as many more. OPC UA contains several modeling and behavior specifications, including Data Access, Historical Access, Alarms and Conditions, and the pub/sub communication model, in addition to supporting specifications like Services, Mappings, Profiles, and Security. The extensibility of OPC UA allows for specifications to be added or changed while mitigating the impact on existing UA-enabled applications.
OPC UA capabilities
UA security
OPC UA helps to enable good security practices for process control and data acquisition for SCADA/HMI and Industry 4.0/Digital Transformation within modern industrial systems.
OPC UA and Industry 4.0
The OPC UA specification facilitates the interoperability and information exchange required for successful Industry 4.0 efforts. Its ability to provide modern, secure cross-platform data exchange, coupled with support for client/server and pub/sub messaging types, creates an opportunity for diverse network topologies and application stacks. Its support for standard and custom information models allows an organization to provide structure to unstructured data as close as possible to the systems generating the data in the model and format that best fits the organization’s unique needs.
