January 2011

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The Meaning of Open
A Simple Answer to a Sometimes Complicated Question.

Andy McMillan Andy McMillan
President and GM
Philips Teletrol
BACnet International
Contributing Editor

A question I hear regularly while talking with customers, prospects and even other suppliers is “What does Open really mean?”   I tend to cringe at the question.  I find it’s a bit like being asked “Do you know the Meaning of Life?”.  Frequently, the person asking the question thinks they already know the answer and just wants to be sure I agree with them.  The problem is that when it comes to the meaning of Open, I generally don’t.  So, at the risk of offending a whole lot of people who have strong opinions and views on this topic, let me offer some of my thoughts on the meaning of “Open.” 

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Standards Approach to Open

Many people define “Open” in terms of number and nature of technical standards that are used in a system.  This line of reasoning generally equates more standards to more Open, but before long devolves to a debate about what exactly constitutes a standard.  Public, consensus standards (like BACnet) are often held up as a paragon of Openness with less public and less consensus standards assuming lesser positions in the Openness hierarchy.  The problem with this approach to exploring the question of “What does Open really mean?” is that it rapidly becomes limited to technical folks with arcane standards knowledge and thus becomes rather irrelevant in the rest of the world. 

Interface Approach to Open

Another approach people often take to “What does Open really mean?” equates Openness to the number of interfaces available in a system design.  In this approach, the assumption is that more is better and even more is even better.  Thus, if every conceivable interface is supported at every level of the system hierarchy then the system must be really, really Open.  There are however, two problems with this approach to understanding Openness.  The first is the assumption that more interfaces are always better.  Of course this assumption is at odds with the reality that complexity is frequently the enemy of quality and always the enemy of security. The second problem with this approach is that it assumes all interfaces at all levels of the system hierarchy are equivalent in the sense that each is weighted equally in terms of measuring the Openness of a system.  As such, this approach does not align well with real-world requirements where quality, security and Openness are all valued, and useless interfaces are not valued at all.

Economic Approach to Open

To find a more useful approach to answering the question “What does Open really mean.?” it is helpful to start with an economic perspective.  The primary impact of “Open” is to reduce friction in the marketplace through lower switching costs, more broadly available substitutes and lower integration costs.  In classical economics reducing friction in a marketplace should result in a more efficient market with better value and generally more options for consumers.  We have all seen it happen in the travel industry.  Travelocity, Expedia and many other sites have made it much easier for consumers to find and book travel, thus dramatically increasing options and value.  It is no different in technology domains.  Just look at the open architecture of IT and the rapid rise in options and value points for computing.  So, rather than talking about standards and technologies, a more useful measure of “Open” in a system is the degree to which it expands useful options and value points for users.  In the building automation world there are several dimensions in which users gain value from expanded options including, mechanical equipment, applications and services

User Value Approach to Open

Looking at Openness from a user value perspective makes it much easier for building owner/operators to evaluate the Openness of systems they are considering.  For example:

1.    In the case of interfaces for mechanical equipment, sensors, actuators and controls, the more qualified sources supported and the greater variety of relevant devices available, the higher the system would score on Openness. 

2.    Support for interaction with relevant applications is another measure of Openness in the user value approach.

3.    Finally, the ability to support relevant service options (such as internal, remote and third party monitoring) is another measure of Openness in the user value approach.

contemporary A couple of caveats are appropriate at this point.  First, note that the technical ability of a system to interact with other devices or applications is necessary but not sufficient to meet the requirements laid out in the three items above.  It is not good enough to know that a system can interface to a third-party device if the system supplier takes the position that actually doing it invalidates a warranty or reduces the supplier’s willingness to assist in system implementation and maintenance.  In the same way, the ability to support independent service suppliers is meaningless if purchasing or contract terms are structured to make third party services unattractive.  This principle is one that I refer to as “Open is as Open does.”  A system is not Open from a user value approach if the system supplier’s business model does not embrace third-party participation in providing solutions to users.

A second caveat has to do with the word “relevant” as used in the three items above.  The user value approach to evaluating Openness does not recognize nor reward interfaces or capabilities that are not relevant to the application and/or the user’s business model.  To use a simple example, a new bowling ball with an Ethernet cable interface might be more Open in the standards approach, and might be more Open in the interfaces approach but is definitely not more Open in the user value approach. 

A final caveat is that while standards per se are not a useful measure of Open, they are still important.  Standards are a necessary tool that enables suppliers to provide users with the options and value points they are looking for.  Any system that does not incorporate standards will necessarily fall short on the Openness scale, but incorporating standards is not a guarantee of Openness in the user value approach.


Too often, Open is evaluated in terms that are not directly relevant to users. Limiting the discussion to specific standards and the processes by which they are developed is not sufficient to guide users.  Looking at the sheer quantity of interfaces is also not sufficient to establish guide users.  An economic approach that looks at increasing user options and value points provides a much better tool for users to evaluate the Openness of systems.

As always, the views expressed in this column are mine and do not necessarily reflect the position of BACnet International, Philips Teletrol, ASHRAE, or any other organization.  If you want to send comments to me directly, feel free to email me at andysview@arborcoast.com.


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