You have probably heard someone talking about Digital Twins in the last few years. You could even say that it has been a buzzword for some time. But since 2019-2020, it's become more than just a buzzword. Organizations and people have started to understand the benefits of having a Digital Twin. There has even been a large increase in organizations that want to start and implement a Digital Twin.

But what is a Digital Twin? I get that question a lot. And every time it is difficult to come up with an answer that others will understand. And even referring to the definition on Wikipedia will not make it easy to understand. There are a lot of different definitions you can find online in articles and blog posts. To explain what a Digital Twin is requires a definition to start with followed by a more in-depth explanation of the definition itself. I use the following definition:

A Digital Twin is a digital replica of entities and their relationships in a reality

You may have noticed that this definition contains several terms: digital replica, entities, and reality. It becomes clearer when explaining each of them in more depth.

Digital replica

A digital replica is a way of storing several entities and their relationships in a specific model. Such a model is stored in a location according to your requirements and needs. An example could be a database or service. Each product on the market that is available to create a Digital Twin has its own way of storing the information that describes the model. That means that the digital replica can describe a real-life situation using definitions and parameters. Think of a machine and whether it is turned on or off. The digital replica would describe the machine and its state. But a digital replica could also be about a collection of machines and their relationships. Think of a machine that is creating a product and the machine that is packing the product. The packing machine requires products to pack anything. That relationship is also described in a digital replica.

Entities

Entities can be different things. An entity can be anything from a physical living being such as people to a physical non-living thing such as processes, machines, buildings, equipment, rooms, and devices. When we talk about physical, it means being physically part of the reality from which you create a digital replica. Each of these entities has a specific purpose within the model. An entity is described by its characteristics that are relevant to the model and what you try to achieve in your solution. An entity could be a temperature sensor installed in a room. The characteristics are then the location of that sensor, the temperature the sensor is measuring, and the notifications it is raising when the temperature gets too low or too high. The location in this case is the room where the sensor is located. That characteristic is a relationship to another entity called the room. All these characteristics when developing Digital Twins are described by properties and metadata.

Relationships

An important part of a Digital Twin is the way entities are related to each other. These relationships are important as they define the context in which the entities are depending on each other and are a part of the reality on which the model is based. A relationship itself defines a set of data based on how the relationship is defined between the entities. An example is the relationship between the temperature sensor and the room where it is installed. This relationship defines what the temperature is within the room. Business rules can be used to take certain actions based on entities and their underlying relationships. An example would be switching off the lights within the room when there is no movement for a pre-defined time. In that situation, the lights, motion sensor, and room are each an entity with underlying relationships.

Realities

Each entity is part of a reality. Normally the reality would be a part of the physical world around us, like the example of the temperature sensor in a room. In that case, we have an actual device, room, and building. But imagine a world that represents a theoretical reality. This could be a virtual, generated reality that acts as the source for the digital replica. An example would be a digital world created in virtual reality or even another Digital Twin.

You have just learned about the concept of Digital Twins and its elements. This is important since it will help you to understand how Digital Twins can be applied to different scenarios. In the next section, we will explore the different parts of the environment around a Digital Twin to implement Digital Twin solutions.

It is important to understand that we need to do more than just store a model of entities to use a Digital Twin. Using a Digital Twin requires us to bind information to our entities in the model and use some method of visualization to view the model and its outputs.

Figure 1.1 – High-level overview of a Digital Twin environment

The model in Figure 1.1 shows a high-level overview of everything that is in some way used within a Digital Twin environment:

• Entities – This part represents the entities from your reality. This is, for example, real-world assets, people, processes, and locations. Data that defines these entities is stored in some way in the Digital Twin.
• Digital Twin – This is the digital replica model of the entities in the reality.
• Input module – This part of the model provides data from entities into the Digital Twin model. In some situations, this is also used to dynamically generate the model-based structure of the entities. It depends heavily on actual data that flows from the entities being used in the reality.
• Output module – The output of the model is in most cases used to visualize the data in some way. But that is not always the case. The output could also be a setting turned on based on business logic and rules that are triggered by the input.
• Business logic and Rules modules – This is all about building logic and rules around the data in your Digital Twin. The result of this logic can resolve into setting the data of entities in the Digital Twin. You could extend this by connecting to or triggering the actual entity.
• Visualize – It is often thought that a Digital Twin is visualized. But that is not always the case. In many situations, the data flows back to the entity itself. But in some situations, a visualization of data could enhance the experience and benefit the business process. Visualization can be reached in many ways. Think of a display at the door of a meeting room displaying availability, an Excel that is filled with output data, or using augmented glasses to create a 3D presentation based on the data from the entities.
• Security – Each module needs to have some sort of role-based security. This can influence what data flows in and out of the Digital Twin. It could be used to only view the data that you are allowed to see based on your role in the organization. But it could also be used to view a subset of output data coming from the Digital Twin.

Now let's look at how a Digital Twin is connected to real-world entities.

A Digital Twin needs to be integrated with the physical and non-physical entities that it represents. As shown in the following figure, you will see that a Digital Twin is about being connected:

Figure 1.2 – Real-world entities are connected to a Digital Twin

Any device that can generate some form of output information based on sensors, processes, or a manual action can be an input for your Digital Twin. And these same devices, if they have some form of interface, can be controlled using rules based on the received input.

Taking the example of the motion sensor, the entity representing the motion sensor needs to get the values from the actual motion sensor in the room. Then, business logic can define that the lights need to be turned off or on based on the value within that entity. The lights themselves are also an entity in the model and bound to the actual lights within the room. The business logic can then set the value on the entity of the lights.

There are Digital Twins that require no visualization. Those Digital Twins handle and set values that will cause certain physical entities to respond. Like the example with turning on and off the lights. There are situations where a Digital Twin needs to be visualized. Such situations require some sort of presentation of the information from the Digital Twin model. Presentations can be flat out a spreadsheet or a list. But they can also be a visual representation of reality on a desktop screen. And nowadays, with extended reality using augmented glasses, it is even possible to have 3D modeled presentations of your Digital Twin.

You have learned about the different modules and parts that are required when you are going to build a Digital Twins solution. In the next part, we will be looking at several real-world examples.