Various industry standards, whether OPC or XML, enhance system interoperability and seamless information exchange. Engineers always need a better way to transfer data from I/O devices to controller datasheets and then to their HMI/SCADA systems. Traditionally, this involves transferring bit modules from remote I/O or other devices over proprietary networks or other low-speed networks. Now, HMI software is increasingly important for factory operational efficiency, and companies are focusing on improving communication between various application solutions and devices from different vendors through standardization. Most newly released automation software is based on Microsoft Windows. Microsoft, in collaboration with experts from various automation vendors, developed Microsoft's Object Linking and Embedding (OLE) technology, which became the foundation of automation information exchange technology. This led to OPC (OLE for Process Control) and the OPC Foundation. OPC DA (data access) is widely accepted in industry, including its application in production control. Tom Burke, president of the OPC Foundation, proposed the standard's "openness, productivity, and connectivity." This standard represents benefits for the entire industrial sector. Joe Rubino, software product marketing manager at Omron Electronics, believes that OPC applications are increasing. "We no longer provide drivers for older or low-cost products. We can use OPC to solve this problem. We are currently working on standardization. The biggest use is data communication between PLCs and operator interfaces. Although users are doing the same data communication, they use the OPC standard for communication from HMI to HMI front-end devices." OPC, based on COM (component object model) and DCOM (distributed component object model) technologies, evolved from OLE and the earlier DDE (dynamic data exchange). Rubino continued, "Based on customer feedback, we understand that COM seems to be static. There are also some concerns about DCOM, particularly regarding connection stability. Disconnections can cause numerous data problems." Even with the widespread adoption of OPC DA and the continuous improvement of other technologies, control engineers and their suppliers are still eager to further explore the potential of OPC DA. The primary reason is the technology's origin from the Internet and the world's wide web. Embedded web pages provide relevant information to the operator interface, along with documentation to aid in maintenance and troubleshooting. Controllers can send emails to engineers and maintenance technicians, but several potential issues remain. Now, the question arises: how best to utilize these technologies? The Internet is entering its third era: from connectivity (FTP, e-mail) to representation (HTML web pages), and now to programmability (XML and related technologies). Networking technologies... Another issue, and a weakness of DCOM, is its difficulty in penetrating enterprise firewalls. Many enterprise IT strategies are related to control engineers, including Internet technologies, where compatibility between new technologies and enterprise IT infrastructure is particularly important. XML (eXtensible Markup Language) is one such technology. It is based on Standard Generalized Markup Language (SGML), developed by IBM Labs in the late 1960s. The commonly used HTML (HyperText Markup Language) is an early version of SGML. These languages ​​have become open, global standards of the World Wide Web Consortium (W3C, http://www.w3.org/). XML is a text-based language, similar to HTML in its use of tags. The difference is that XML tags describe the type and nature of information, while HTML tags describe how the page is displayed when accessed by compatible browsers. XML tags sometimes resemble product names, output variables, serial numbers, storage quantities, etc. In fact, XML is just one software technology; a universal method is still needed to be found that can be used for information transfer between devices, platforms, and regardless of hardware or operating system. Other technologies include the Extensible Style Sheet Language (XSL), which tells computers how to format XML information for browsing; Document Type Definition (DTD), which defines the rules for a type of document; and Simple Object Access Protocol (SOAP), which defines an XML data "message" that can be transmitted over a network. The initial OPC XML implementation followed this method: OPC data went from field devices to HMI/SCADA software, while XML data went from the HMI to commercial software, or from the HMI to the operator interface browser. SOAP is a "lightweight" information format that works on any operating system, platform, or programming language. It integrates XML information and requires a transport structure, such as HTTP, to deliver the information to the client. Combining OPC and XML Since OPC has become a viable standard for control information exchange, it only needs to continuously expand its Internet compatibility. So why can't OPC and XML be combined? Members of the OPC organization began considering this issue two or three years ago. The technical committee has begun hard work on standard development. Don Holley, Vice President of Marketing at the OPC Foundation, believes that the committee is already continuously developing and shifting the process to Microsoft .NET. You can enable an existing OPC data access XML server and connect it to the Internet, or you can build an XML .NET server without COM/DCOM. We know that enterprises prefer to receive information from XML rather than COM/DCOM. Jim Luth, a member of the OPC/XML committee, believes the slow release of the OPC/XML specification is due to XML being a text file, unlike COM (which is similar to C++). He argues that a good way to implement standards is to obtain tools from the Microsoft .NET platform. While many vendors use COM for non-Microsoft platforms, XML will allow for earlier integration with advanced commercial systems. Larry Bible, Marketing Manager at USDATA, believes that OPC's implementation of HMI/PLC connectivity is a significant advancement. It allows the software industry to focus on HMI development. Currently, XML handles the top of the information pyramid, while OPC handles the lower levels. The Importance of OPC: Bernie Anger, Vice President of Software Development at GE Fanuc, points out, "The biggest challenge for OPC is that it needs to run on a PC. The most exciting news about XML is that we now have OPC servers and clients that support any Internet XML, enabling next-generation communication. For example, controllers will support OPC X, allowing direct communication between PLCs and Internet browsers." Paul Camuti, General Manager of Industrial Software at Siemens E&A, believes that OPC plays a crucial role in the industrial sector. From a supporting technology perspective, the purpose of OPC DA is to reduce the cost of integrating completely different control systems. Not long ago, integrating HMIs and control systems was quite expensive, and the reuse rate of these software components was relatively low. With the introduction of these standards, the cost of connecting them will be significantly reduced. OPC continues to dominate the automation industry. This is related to OPC DX (data exchange). In systems combining fieldbus and Ethernet, OPC DX is a significant factor in overcoming communication barriers and improving the interoperability of systems from different vendors. The DX standard provides interoperable data exchange and server-to-server communication over Ethernet. A key aspect is that each major fieldbus, including FOUNDATION Fieldbus, Profibus, ControlNet, and DeviceNet, has its own Ethernet gateway. This is akin to the Babel Tower of Ethernet – chaotic and inefficient. In contrast, OPC Foundation members found that users could benefit without disrupting a significant amount of existing work. ARC Vice President Dick Caro believes this is one of the biggest news stories of the century. Why? Because Siemens, Rockwell, and other major bus vendors are joining the fray. This could very well be the final solution to the bus wars. John Baier, Software Architecture Manager at Rockwell Software, explains that OPC DX and OPC XML each have their own functionalities. DX allows peer-to-peer messaging between OPC servers, allowing users to adopt the existing OPC DA protocol. While OPC DA is already used between HMI clients and OPC data servers, OPC DX now adds the ability to share data between OPC servers. XML is a new standard that allows OPC or factory-level data to be accessed via standard XML web servers. Customers can obtain data from OPC servers using OPC XML, and this can bypass firewalls. OPC DX uses Direct XML technology, instead of OPC XML, to configure servers. As a vendor of OPC XML, servers can easily exchange data using OPC XML. This allows small devices to execute OPC XML independently, rather than having to support all OPC protocols. In the coming years, the visibility of direct network access devices will increase, from PLCs to small devices. This is known as the third generation of the Internet. The earliest generation was connectivity and simple text communication. The second generation was network and information display, such as web pages. The third generation is information exchange on the Internet. XML is the third-generation language. Peter Wengert, an industrial manager at Microsoft Corp., believes that current XML and web services are expanding not only on the Internet but also deep into the factory floor. Developers can use the same technology for control, HMI, ERP, and supply chain. The advantage of other practical open standards is that large companies have a wide range of products to develop, and small companies also have many excellent ideas. Software Toolbox offers a suite of ActiveX controls for OPC instruments, enabling the creation of operator-defined interfaces and access to enterprise-level OPC servers. As businesses develop broader perspectives, such as "We need to integrate real-time, factory-level data into our enterprise systems to improve customer support and reduce costs," these tools will help you solve many problems.