> 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-how-it-works/selmo-training/chapter-4-the-ptf-principle-process-technology-function.md).

# Chapter 4 – The PTF principle (Process – Technology – Function)

**Summary:**\
Chapter 4 describes the methodological foundation of Selmo.\
The **PTF principle** shows how a real process becomes a complete, logical model:\
The *process* defines the states,\
that *technology* describes the hardware used,\
and the *Function* specifies which actions and feedback are represented in the control.\
The chapter makes clear: Only when all three levels are described cleanly does a complete SEQ emerge.\
Thus PTF is the entry point of every Selmo project – the bridge between idea and implementable model.


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