> For the complete documentation index, see [llms.txt](https://infosys.selmotech.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://infosys.selmotech.com/selmo-solution/selmo-solution-en/selmo-documentation/3-the-selmo-method-ptf/digital-twin-as-a-conceptual-model.md).

# Digital Twin as a conceptual model

## 3.2 Digital Twin as behavior model

This chapter clarifies, **what a "Digital Twin" means in the context of Selmo**\
— and what explicitly **not**.

It creates a clear conceptual basis\
so that the Selmo model is correctly classified.

***

### The term "Digital Twin" — a need for clarification

The term "Digital Twin" is used today for very different things:

* 3D visualizations
* simulations
* virtual commissioning
* marketing representations
* data replicas of real machines

This multiplicity of meanings leads to misunderstandings.

Selmo uses the term **deliberately restricted**\
and **precisely defined**.

***

### What the Digital Twin is in Selmo

In Selmo the Digital Twin is:

> **A digital representation of the expected machine behavior.**

Specifically this means:

* the twin describes **states**
* it describes **expectations**
* it describes **monitoring**
* it describes **reactions to deviations**

The Digital Twin in Selmo is:

* formal
* deterministically
* be verifiable
* explainable

It describes **not the machine**,\
but **its correct behavior**.

***

### What the Digital Twin in Selmo is not

The Selmo Digital Twin is **not**:

* a 3D model
* a physical simulation
* a virtual test system
* a substitute for real commissioning
* a marketing artifact

It does not replace:

* no mechanical design
* no safety analysis
* no validation of the real technology

> **Selmo models behavior,**\
> **not geometry or physics.**

***

### Relationship between reality and model

The Selmo Digital Twin has a clear relationship to the real machine:

* The real machine **executes**
* The Digital Twin **describes what is correct**

The twin:

* defines target states
* defines allowed transitions
* defines valid conditions

The real machine:

* is measured against it
* is monitored against it
* is diagnosed against it

> **Deviation means:**\
> **Reality deviates from the modeled behavior.**

***

### Digital Twin and determinism

Since the Digital Twin is modeled formally:

* there is a unique state at every point in time
* expectations are explicitly described
* reactions are defined

This means:

* no interpretation-dependent behavior
* no implicit assumptions
* no situation-dependent logic

> **The Digital Twin is deterministic —**\
> **otherwise it would not be verifiable.**

***

### Digital Twin as a basis for operation and diagnosis

The Digital Twin is the basis for:

* Process control
* state management
* model-based diagnosis
* consistent HMI display
* automatic documentation

HMI and diagnosis show:

* not "what is happening right now"
* but **how reality relates to the model**

***

### Distinction from simulation and virtual commissioning

Simulations answer:

* *What happens if...?*

The Selmo Digital Twin answers:

* **What may happen?**
* **What is expected?**
* **What is correct behavior?**

Both can complement each other,\
but are **not the same**.

***

### Role of the Digital Twin in the overall Selmo approach

The classification is clear:

PTF\
↓\
Digital Twin (behavior model)\
↓\
Selmo model (formalized)\
↓\
Real machine

The Digital Twin:

* originates from analysis (PTF)
* is formally described in the Selmo model
* remains valid during operation

***

### Summary

The Digital Twin in Selmo is:

* a formal behavior model
* not a simulation or visualization concept
* Basis for monitoring, diagnosis and responsibility

> **Selmo does not use the Digital Twin**\
> **to show the machine —**\
> **but to make it explainable.**


---

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