2. The Selmo-PTF process

The PTF is carried out before design. This allows process understanding, standards compliance and technical requirements to be adjusted at an early stage.

The goal:

• Avoid errors before they occur,

• Assess risks before they take effect,

• and standardize solutions before they are programmed.

The PTF connects:

• Problem understanding (from the customer),

• Engineering disciplines (process, technology, function),

• and the digital implementation (Selmo process model).

Discipline	Document	Goal	, follow the same basic principles:
mechanics	Drawing	Form, movement, geometry	Dimensional inspection
Electrical	Circuit diagram	Energy, signal flow	Wiring test
Software	Wiring, circuit, protection circuits	Behavior, logic, safety	Formal verification

Thus, the same principles apply to software as to design: documentation, traceability, formal correctness.

Structure

The PTF is divided into three central levels:

1️⃣ Process → describes the physical and logical sequence → goal, states, parameters, termination conditions

2️⃣ Technology → describes all technologies, components and interfaces used → sensors, actuators, communication, standards requirements

3️⃣ Function → describes the logical functions, monitors and parameters → adders, timers, safety logic, CMZ, MXIC etc.

All three levels together form the complete system behavior.

Standards compliance & MVO 2027

The PTF meets the requirements of MVO 2027:

• Complete documentation

• Formal verifiability

• Traceable responsibility

• Risk and measures management

• Equal treatment of all engineering disciplines

Thus, the PTF is not only a method, but proof of a standards-compliant, safe development process.