Gemini Principles for Digital Twins

I recently took a swing at describing my version of a digital twin. At the time, I wasn’t aware of much prior art other than the typical hype cycle. Recently, I was pleasantly surprised to come across a framework for digital twins developed by Centre for Digital Built Britain. More specifically, the Digital Framework Task Group has published a report outlining a common set of definitions and principles related to the development and use of digital twins. Termed the Gemini Principles, this report outlines nine key principles within three groups of purpose, trust, and function.

Purpose

Leading off, we see that a digital twin must have a clear purpose. The three principles that define the purpose include Public good, Value creation, and Insight.

Public Good

From the text:

“Must be used to deliver genuine public benefit in perpetuity”.

My take:

This is a great start. If a digital twin isn’t going to benefit its consumers, then why expend the effort to create and maintain it?

Value Creation

From the text:

“Must enable value creation and performance improvement”.

My take:

This principle drives at a key question when discussing digital twins - “What do I get?”. And the answer here isn’t one-size-fits-all. Digital twins need to be flexible and tailored to specific use cases and needs - often most clearly identified as “pain points” within the current state of an entity or process. The second part of this principle points to a common use case where an effective digital twin will improve performance as measured by key indicators such as percentage of a transit system’s on-time service or pavement condition over time relative to what was predicted by the mix design.

Insight

From the text:

“Must provide determinable insight into the built environment”.

My take:

This has been my go-to term when making the case for infrastructure digital twins. A primary challenge in maintaining the built environment is that much of the critical components are hidden out of sight. In a building, drywall conceals the framing and electrical wiring. On a bridge, the rebar is invisible underneath its concrete encasement. Stormwater drainage systems operate by gravity and therefore have to be underground to be of much use. Capturing all of that information in a digital twin provides “X-ray vision” of these hidden components via 3D viewers and Virtual Reality or Mixed Reality environments. In the bridge example, an inspector can see a surface crack in a column and correlate its physical location to the as-designed or (preferably) as-built reinforcement model within the digital twin. The criticality of the observed cracking as it relates to overall structural integrity can then be assessed in real-time without having to return to the office to track down record plans on microfiche.

Trust

Next, we see that a digital twin must be trustworthy. Trustworthiness is demonstrated by Security, Openness, and Quality.

Security

From the text:

“Must enable security and be secure itself”.

My take:

As digital citizens of the 21st century, we can all understand the need for security, even when it comes at the cost of convenience. It can be frustrating to have to reach for a hardware key when two-factor authentication is required, but the internet never forgets and you can’t put the toothpaste back in the tube after a data breach.

Openness

From the text:

“Must be as open as possible”.

My take:

Data wants to be free, and no one should be excluded from the benefits of a digital twin just because they haven’t bought in to proprietary systems or aren’t running a mainstream operating system. The Information Age is founded upon open standards such as TCP/IP and HTML and a digital twin should be no different.

Quality

From the text:

“Must be built on data of an appropriate quality”.

My take:

This immediately makes me think of Level of Development (LOD) when used in the context of Building Information Modeling (BIM). If you are going to fabricate replacement parts based on the geometry stored in the digital twin, then that data had well better meet LOD 350 or higher. Conversely it is possible to have too much of a good thing. Geometric detail requires more bytes per unit of physical asset and these storage needs may not scale well across a huge system such as a statewide transportation inventory.

Function

Rounding out the Gemini Principles, we see that a digital twin must function effectively by providing Federation, Curation, and Evolution.

Federation

From the text:

“Must be based on a standard connected environment”.

My take:

Again, my mind goes to the division of information within a BIM environment. Each design discipline is responsible for modeling their portion of the work, be it structural, electrical, civil, etc. These models are then connected and combined into a common data environment where clash detection can be performed and the proposed work can be evaluated as a whole. This principle also applies to the Operations and Maintenance phase. For example, a department of transportation may have responsibility divided between organizational units focused on bridges, pavements, environmental resources, ancillary structures, and other subsystems. Too often data is siloed and constrained by blockage between disparate systems. An effective digital twin eliminates blockage and allows for frictionless information sharing across all participants.

Curation

From the text:

“Must have clear ownership, governance and regulation”.

My take:

Absolutely! In my career I’ve experienced this need most often when sharing CAD data. Downstream users tend to distrust any information provided by a third party and governance is typically managed informally via handshake agreements. I’ve also experienced curation done well when consuming aerial imagery and digital elevation models that contain metadata identifying the party that generated the information and outlining its permissable use. More recently I’ve noted that open data portals tend to provide clear curation information that is standardized and accessed just as easily as the data itself.

Evolution

From the text:

“Must be able to adapt as technology and society evolve”.

My take:

The text mentions that the Gemini Principles are “descriptive of intent but agnostic on solutions”. Nowhere is this seen more clearly than in this final principle. A digital twin doesn’t have to chase fads or constantly be reinvented in the latest javascript framework flavor of the month. It does have to evolve to meet additional maturation of technology. A great example is the (relatively) recent shift from traditional desktop machines to mobile devices. Responsive layouts have emerged to meet the users where they are, and there are certain to be new challenges and innovations in the future that will shape the format and delivery of digital twins. My guess is that the next big shift will involve widespread adoption of augmented reality devices and the patterns that form for effective and efficient user experiences with this type of hardware.

Wrapping up

So there it is - a nice symmetry of 3 groups of 3 principles each. Short enough to be easily digested while open-ended enough to guide discussions and drill down to the value that a digital twin will provide - whatever the use case or user base. I’m grateful for the work done by the Centre for Digital Built Britain and all contributing individuals that had a role in developing this guidance. It has certainly helped me personally in providing a framework of understanding around the nebulous concept of digital twins and I’m equally certain that it will continue to be of good use in the future when seeking to develop digital twins as a means of value creation as opposed to bandwagon jumping.