The ISO answer to what is a digital twin

[edit] Digital twin definition

For at least the past five years, the built environment, as well as other economic sectors, have been investigating ways of using digital twins. However, several activities to bring stakeholders together have been thwarted by a lack of consensus in relation to what a digital twin is.

In earlier 2024, BSI, the UK’s national standards body, published as BS ISO/IEC 30173. This standard looks to formalise some of the key concepts which constitute what a digital twin is, as well as some key terms and definitions.

So, what is a digital twin? BS ISO/IEC 30173 provides a definition: digital twin: digital representation of a target entity with data connections that enable convergence between the physical and digital states at an appropriate rate of synchronisation.

Whilst this definition is helpful, it is also quite complex. So, let’s break it down.

[edit] Target entity

The target entity, simply put, is the subject of the digital twin. The standard describes these as being ‘real’ things like components, assets, systems and processes. The subject is then observed through data connections like sensors.

[edit] Digital representation

The digital representation is the digital version of the target entity. Depending on the subject, the way it is represented may change. It may be useful to represent the shape of a component graphically (i.e. a 3D model), but a process or system may need to be represented more conceptually (e.g. as a diagram or a model notation). Much like with Building Information Modelling (BIM), digital twins aren’t about 3D models, they are about the exchange of pertinent information.

[edit] Convergence

Perhaps subtly the most significant part, Convergence is the act of coming together. In this instance, convergence can be achieved in three different ways:

1. The digital representation changes to reflect the target entity (e.g. a component, which is being tracked, is moved. Once in its new position, its location is updated with new coordinates).
2. The target entity changes to reflect the digital representation (e.g. someone sets a thermostat which is monitoring a living room. The thermostat triggers the room to warm up).
3. Both the digital representation and target entity change to meet in the middle (e.g. a complex algorithm behind a series of interconnected digital twins may influence several entities and representations concurrently).

[edit] Appropriate rate of synchronisation

This is the idea that convergence occurs as often as needed. For cases relating to life safety, near real-time may be a requirement. For other use cases, this convergence might happen less frequently.

[edit] So, is [X] a digital twin?

Let’s use an example: the Met Office Weather Map. If I go to the Met Office website, I can see a digital

representation of the UK weather system in the form of an interactive map. Weather stations provide a data connection by sending weather data to the Met Office’s Weather Observations Website. This data connection allows the data behind the interactive map to converge with observed data at an hourly rate. As such, it appears that the Met Office Weather Map is a digital twin, as defined within the standard.

There we have it. Hopefully, standards such as BS ISO/IEC 30173 will provide the support needed to help stakeholders come together to talk about digital twins in a more consistent manner. In doing so, we can look to advance their application within the built environment.

This article appears in the AT Journal issue 150, summer 2024 as 'Has ISO answered the question, “What is a digital twin”? and was written by Dan Rossiter FCIAT, Built Environment Sector Lead, BSI.

--CIAT

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