The fundamental problem of today's machine logic

1.2 The core problem of today's machine logic

The central problem of modern machine controls is not a lack of technology and also not a lack of programming competence.

The core problem is that machine logic today exists predominantly implicitly.

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Implicit logic

In classical controls logic arises:

• distributed across many code locations

• as a combination of conditions, linkages and side effects

• often dependent on order and context

Machine states are:

• not explicitly defined

• not formally described

• only indirectly derivable from the code

This means:

The machine “knows” what it is doing – but no one can clearly read it off.

Logic exists, but it is not visible.

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Code ≠ Documentation

Traditionally it is assumed:

“The code is the documentation.”

In simple systems that may be true. In complex machines, however, this assumption leads to a rupture.

Typical symptoms:

• Documentation describes an ideal state

• the code continues to evolve

• deviations are not propagated

• Comments explain how, but not why

The code shows:

• current signal linkages

• implementation details

It shows not:

• which states are intended

• which conditions are mandatory

• what behavior is expected

Code describes implementation – not meaning.

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Lack of traceability

From implicit logic and lacking formal documentation a fundamental traceability problem arises.

Typical questions are hard to answer:

• What state is the machine currently in?

• Why is it waiting?

• What is missing for the next step?

• Why is a movement being prevented?

• Which condition currently has priority?

Answers to that:

• depend on the person

• require experience or code knowledge

• are often not unambiguous in case of error

This has concrete consequences:

• diagnosis becomes vague

• changes become risky

• safety becomes hard to argue

• responsibility can hardly be demonstrated

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The actual deficit

The actual deficit is not the code.

The deficit is:

the absence of an explicit, formal model for the expected machine behavior.

As long as behavior exists only implicitly:

• it cannot be verified

• it cannot be automatically diagnosed

• it cannot be reliably documented

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Transition to the stance

The consequence of this finding is clear:

machine logic must visible, unambiguously and be verifiable .

This demand is the starting point of the Selmo stance.