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“Open” BMS is not just about protocols: Schneider Electric

“Open” BMS is not just about protocols: Schneider Electric
A whitepaper proposes a logical framework that would help businesses better understand open BMS. This framework consists of three layers that define the concept of open.
The term “open” has become quite popular in recent years. From open architecture in VMS to open protocols that allow integration of different brands, the concept suggests inclusiveness, which is good both for businesses and customers.
But in the building management systems industry, the word open refers to something much more than protocols, according to Wendy Torell, a Senior Research Analyst at Schneider Electric’s Data Center Science Center.
“The term “open” is often used to describe desired functionality of a Building Management System (BMS),” explains Torell in a blog post on the company website. “It is thought to be essential in achieving the ambition of a smart building. But interestingly, that term itself, while often used by building owners/operators as requirements for their system, as well as by vendors to describe attributes of their systems, generally creates much confusion and ambiguity since the industry lacks a standard definition.”

Developing a framework for open BMS

In a recent white paper published along with her colleagues at Schneider Electric, Torell proposes a logical framework that would help businesses better understand open BMS. This framework consists of three layers that define the concept of open. Each of these layers presents certain expectations that an open BMS needs to meet and build on top of one another.
“This means the capabilities from layer 1 are pre-requisites for achieving the capabilities of layer 2, and layer 2 are pre-requisites for achieving layer 3,” Torell says. “For each of the three layers in the framework, we have defined three criteria for assessing how open the system is: (1) Interoperability, (2) Engineering complexity, and (3) Who performs the work.”
As the name suggests, interoperability evaluates how well one component of a BMS operates seamlessly with another or how well one system works with another. Engineering complexity refers to the level of difficulty to achieve this interoperability. The third criterion checks if the people who operate the BMS need specialized training, making things difficult for customers.
 Torell added that there are often tradeoffs with these criteria. For instance, you might be able to achieve a highly open system in terms of interoperability by sacrificing engineering simplicity; or work can be done without engineering complexity, but only by a vendor’s certified technician. Having this construct for discussing a BMS’s degree of “openness” brings these important topics and tradeoffs into the picture.

The three layers

The first layer of the proposed framework is data acquisition and sharing. This is critical to any BMS because sensors that send data and receivers that capture and process them form the foundation of a smart building.
“Controllers require protocols to communicate,” Torell said. “More and more, controllers use open protocols, and to consider a BMS open, it should be interoperable across multiple OT protocols (i.e., BACnet, LonWorks). But just because it uses an open protocol doesn’t mean it is interoperable. The needed data must be exposed by the vendor. The system should also support the extension of native protocols, in order to limit the number of gateways required to serve as “translators” to the sensors, actuators, and controllers.”
The second layer is integration, as BMS solutions extend beyond their conventional role to work alongside security, safety, and other segments. An open BMS solution should allow standard protocols that enable integrators and customers to unite all their solutions and operate them together. Finally, the third layer is building orchestration, which refers to the efficient coordination of all systems under the BMS.


As systems like BMS continue to develop, there is definitely a need to define their role and functions clearly. Knowing what constitutes an open BMS would help customers make better purchase decisions. Other segments like surveillance and access control would also benefit from considering this kind of framework.
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