What is Selmo?

Selmo is a model-based standard for describing the behavior of machines and systems.

The focus is not the code, but:

• States

• Expectations

• monitoring

• Reactions

From this model arise:

• PLC code

• HMI structures

• diagnosis

• Documentation

Not separated, not afterwards – but from the same source.

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What Selmo is not

To clarify:

Selmo is not:

• a PLC programming standard

• a framework with best-practice building blocks

• an AI autopilot for machines

• a replacement for safety controllers

• a UI or HMI concept

Selmo does not replace no responsibility. It makes responsibility visible.

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Why Selmo exists

Modern machines are:

• complex

• highly automated

• legally relevant

• safety-critical

At the same time, their logic is often:

• implicit

• distributed in the code

• hard to explain

• barely verifiable

This leads to a fundamental problem:

Code describes what happens – but not why it is allowed to happen.

Selmo exists to answer this “why” formally.

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The basic attitude of Selmo

Selmo is based on few but strict principles:

Model before code

Code is an implementation. The model is the truth.

Explicit instead of implicit

What is relevant is modeled. What is not modeled does not exist.

Determinism

At any time it is clear:

• which state is active

• what is expected

• how it reacts

Behavior instead of signals

Signals are physical. Behavior is functional.

Responsibility through traceability

What can be explained can be verified. What can be verified can be held responsible.

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How this documentation is structured

This documentation follows two lines of thought:

Analytical – from the problem

Why classical machine logic reaches its limits and what requirements arise from that.

Synthetic – toward the model

How Selmo structures machines:

• Plant

• Hardware zone

• Sequence

• Zone

• Bit control

• CMZ

Every content exists only once. Cross-references replace repetitions.

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One last thought

Selmo does not make machines simpler. It makes them clearer.

Clarity is demanding. But it is the prerequisite for:

• Safety

• Scalability

• Responsibility

• Trust

Selmo forces clarity – so that machines remain explainable.