OPC

What is OPC?

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History of the OPC standard In 1995, four providers of industrial automation solutions created a working group to standardize the data access protocols of their devices, which at that time mostly used the Microsoft operating system. The objective was to summarize the communication protocols of programmable logic controllers (PLC/PLC). The working group, by summarizing these different protocols, was able to create a standardized interface that works as a middleman. This interface converted read or write requests between the human-machine interface used by operators to control machines via PLC and SCADA (Supervisory Control and Data Acquisition). In 1996, the working group released version 1.0 of the standard, called OPC (later renamed OPC Classic), which other hardware and software vendors began to adopt. The same year the OPC Foundation is created in order to formalize the compliance, certification, interoperability and validation procedures. OPC Classic Specifications The first version of the OPC standard was based on a Microsoft technology for exchanging data between software components called DCOM (Distributed Component Object Model), a subset of COM (Component Object Model). The original meaning of OPC was “OLE for process control”, OLE (Object Linking and Embedding) which refers to a Microsoft COM technology designed to embed and link documents and other software objects. In 1998, the OPC Foundation began converting the initial specification to web services. There are three specifications of OPC Classic: -OPC Data Access (OPC DA) defines OPC client-server technology and how software can read and write data, as well as the available data types and structures. -OPC Alarms and Events (OPC AE) describes the procedures by which OPC server software can monitor systems and send alarms to client software. -OPC Historical Data Access (HDA) defines queries and analysis that can be applied to time-stamped historical data provided by devices. OPC UA

Unified OPC architecture In 2008, after Microsoft began to put less emphasis on DCOM and help OPC software vendors adopt non-Windows devices, the OPC Foundation released the currently enforced standard, OPC Unified Architecture (OPC UA). It is backward compatible with OPC Classic and is based on service-oriented architecture (SOA), a software design approach now more widely used in manufacturing systems. OPC UA is an extensible SOA framework, designed to support a wide range of platforms, from embedded microcontrollers to cloud infrastructure. Manage security through encryption, authentication, and auditing features. It goes beyond OPC Classic by adding features on demand, the ability to discover servers and other systems on a network, and an address space scheme designed to allow more complex data to be used. The OPC base provides a set of proxy wrappers (responsible for transcoding OPC UA messages into COM/DCOM messages) to allow components using the OPC UA model to integrate with OPC Classic components (using the COM/DCOM/OLE model). ). At the end of 2017, the OPC Foundation had 470 member companies, based around the world. These members are leading players in software, hardware, industrial automation, machine-to-machine (M2M), energy efficiency, and batch and continuous manufacturing. The best known are Honeywell, IBM, Microsoft, Pfizer, Rockwell, Samsung, SAP and Siemens. In recent years, IIoT (Industrial Internet of Things, Industrial IoT) technology providers have used the OPC UA standard in product demonstrations. In 2016, the OPC Foundation announced a partnership with the Object Management Group and its program, the Industrial Internet Consortium, to integrate the two standards for IIoT.
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