For years, ARC has been espousing on the importance of standards. We classify standards into three fundamental groups: formal industry standards; de facto (open) standards that have not yet been sanctioned by one or more industry bodies; and proprietary (closed) standards. Formal standards, such as those defined and sanctioned by international standards bodies such as ISA, IEC, and IEEE, promote choice. That’s because multiple suppliers and technologies will utilize these, providing more choice for the user. De facto standards tend to limit choice, since while they are open and available to all, they are often supplier-specific. Microsoft Windows is an oft-cited example. While this open technology is widely used in the automation systems market, the fundamental system technology is only available from one company – Microsoft, limiting choice. The third type of standard, proprietary, further eliminates choice, since it is closed and only applies that specific supplier’s technology.
Complex process automation systems typically use all three kinds of standards to various degrees. For example, truly open standards such as 4-20 mA for analog I/O signal communication, allows transmitters and actuators from a wide range of suppliers to be connected safely. Digital fieldbus communications, such as FOUNDATION fieldbus and Profibus have also been recognized as full standards by industry organizations and embraced by many different suppliers and end users alike
However, it’s important to understand that, while many distributed control systems (DCSs) on the market utilize full standards such as Ethernet (IEEE 802.3) for their controller LAN communications, the standards apply only to the lowest two layers of the OSI protocol stack, providing proprietary protocols for the top layers.
In our everyday lives, we take for granted such widely adopted standards as 110V 60Hz AC electricity in our homes (in North America at least…), driving on the right side (except for a few countries), and standard IEEE 802.11 Wi-Fi for our mobile devices. Of course, widely accepted standards sometimes must be modified or replaced with even better standards that meet a broader need. For example, although public switched telephone network (PSTN) are still in use, for many these are being replaced with voice over internet protocol (VoIP). But the user of a telephone doesn’t need to know which protocol is carrying your voice signal to make a call. This is what formal standards provide.
Ultimately, whenever the selection of a standard in our system technologies restricts choice, it comes with a price. Most often that price is flexibility and lifecycle cost.