> 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-structure-and-standard/selmo-technical-standard-and-structure/selmo-method-in-practice/method-the-selmo-ptf-process.md).

# Method: The Selmo PTF process

### 1. Introduction

The **PTF process** Selmo (Process – Technology – Function) describes the methodical approach taken before a process model is created and automated code is generated. It ensures **clarity, consistency and traceability** and thus forms the foundation of the entire Selmo approach.

***

### 2. The three levels

#### 2.1 Process (P) – Sequence and logic

* Definition of the **logical sequence**
* Description of all **states and transitions**
* Modeling of a **state machine**

👉 Result: A clear understanding of the process, independent of technical details.

#### 2.2 Technology (T) – Components used

* Analysis of the **available hardware** (sensors, actuators, interfaces)
* Definition of the **operation and characteristics**
* Assignment of the **measurement and control signals** to the process

👉 Result: The process is linked to the real technology.

#### 2.3 Function (F) – Building blocks of implementation

* Identification of the required **functions** (e.g. adder, cylinder control, test module)
* Clear description of **inputs, outputs, limits and behavior**
* Functions are **encapsulated, reusable and testable**

👉 Result: Building blocks that can be cleanly integrated into the process.

***

### 3. Interaction of P, T and F

* **process** describes the “when” (sequence, state changes).
* **technology** defines the “with what” (components, interfaces).
* **Function** determines the “how” (concrete implementation).

This separation provides:\
✅ Clarity in design\
✅ Transparency in operation\
✅ Safety and efficiency when making changes

***

### 4. Practical example: The flap

Let’s take a **flap**that is to open and close:

1. **Process level**:\
   – Logic: “When part is inserted → close flap; after processing → open flap.”\
   – The sequence is unambiguously described in the model.
2. **Technology level**:\
   – Flap cylinder, limit sensors, possibly jam sensor.\
   – Sensor reports “0 = free.”
3. **Function level**:\
   – Function “close flap”: issue signal → cylinder moves → wait for feedback.

***

#### The deviation in reality

Although the sensor reports “0”, a **backlog** may be present → the flap is blocked.

* In the **Model** is defined: “close flap.”
* In **Reality** it does not happen.
* Selmo recognizes: **deviation between target and actual**.
* Immediately a clear message appears on the **HMI**: *“Flap zone – deviation”*.

***

### 5. The effect of the PTF process

* The process is described clearly and deterministically.
* Deviations in reality become immediately visible.
* Errors are **transparent, analyzable and quickly removable**.
* Iterative changes (hardware, process) can **be specifically traced back into the model** and remain consistent.

👉 In this way the PTF process connects **formal rigor** with **practical manageability**.

***


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