Mechanism of Operation vs System Model vs Diagram

Introduction

During analysis, we often use the term ‘model’ and less frequently the term ‘mechanism’. The term “mechanism” when we want to explain something, such as “the mechanism for generating a discount on an invoice.” ”

But here beware: the model (block diagrams, formulae, etc.) is documentation and a copyrighted description. The mechanism is what we understand by reading this documentation (model), as the mechanism is protected know-how. The content of the application to the Patent Office is the model (description), but what we patent is the invented/developed mechanism.

Keywords: model, mechanism, diagram, UML

Mechanism vs. model

Mechanism and model in science are close concepts. For example, they are described as:

Modeling involves abstracting from the details and creating an idealization to focus on the essence of a thing. A good model describes only the mechanism. [Glennan argued that mechanisms are the secret connection that Hume sought between cause and effect: “A mechanism of behavior is a complex system that produces that behavior through the interaction of many parts, where the interaction between the parts can be characterized by direct, invariant generalizations relating to change” (Craver & Tabery, 2019)

Let’s examine how these terms are defined by the official Dictionary of the Polish Language:

Mechanism: “the way something is formed, runs, or operates.”
Model: “a construction, scheme, or description showing the operation, structure, features, relationships of some phenomenon or object.” “

Dictionary of the Polish Language (https://sjp.pwn.pl/)

As you can see, very similar but not identical. The term “diagram” is defined in English literature as:

Diagram: a simple plan showing a machine, system, or idea, etc., often drawn to explain how it works.

(https://dictionary.cambridge.org/)

In the scientific (English-language) literature, the concept of modeling is defined as follows: to

model something is to create a copy or description of an action, situation, etc., so that it can be analyzed before proceeding with the real action.

https://www.oxfordlearnersdictionaries.com/definition/english/model_2?q=modeling

Graphically, this conceptual model can be illustrated as a diagram:

Concepts: diagram, model, and mechanism, and the areas of law governing them. (Author’s own)

There remains the question of concepts: the phenomenon (which we want to describe and explain) and its explanation. A given phenomenon is a certain observed fact. Most often, we describe it literally or create statistics about it. Craver illustrates the relationship between the phenomenon and the mechanism of its formation in this way:

The upper ellipse represents our observations of stimuli and effects, and the ellipse is a record of the facts and their statistics. Statistics, however, is not a model, it is only a statistic, a collection of data about the facts, it does not provide any explanation for their formation.

The lower ellipse represents the mechanism that explains the formation, initiated by stimuli, of the observed effect (facts collected in statistics). It is an explanation of how the effect (facts, effect) arises and is the mechanism for the emergence of what we observe. We illustrate (can be expressed as) this mechanism (explanation) as a model, which can be expressed, for example, by a flowchart.

Examples

An example that everyone is probably familiar with is Copernicus’ Theory. The diagram shows: top left, a record of observations of the heavens, wrongly called a (statistical) model. These are the so-called epicycles (below left): a depiction of observations of the paths of planets and stars in the sky, observed from Earth. On the right, the heliocentric solar system diagram is a model that explains the mechanism of epicycles or loops that the observed stars and planets make in the sky.

Watt Regulator

Another example is the Watt regulator. Below is a model of this regulator:

The original schematic is Watt’s regulator, describing its design.

The description of the mechanism in the patent application was text similar to this:

If the machine is at rest, then the weights (balls) are at the very bottom, and the throttle is fully open. If the steam machine starts working, the rotating wheel of the steam machine is connected to the speed regulator, the balls begin to rotate. Two forces act on the balls of the regulator: the gravitational force attracting the balls vertically downward and the centrifugal force pulling the balls outward, which, with this design of the regulator, causes the balls to float upward. The rising balls cause the throttle to close, and this resulted in less steam being supplied to the steam engine. The machine slows down, so the centrifugal force decreases, the balls fall down,soandthe throttle opens, thus supplying more steam to the machine.

https://pl.wikipedia.org/wiki/Regulator_od%C5%9Brodkowy_obrot%C3%B3w

Diagram describing this regulator:

Diagram describing the mechanism of the Watt Regulator.

The mechanism that explains the operation of this regulator is a negative feedback system (Bertalanffy, 2003):

Negative feedback as a mechanism to explain the operation of the Watt regulator.

Watt’s regulator is precisely the negative feedback. In the diagram above, PROCESS is a steam machine. The quantity at the input is steam with a certain pressure, and the quantity at the output is the speed of the drive shaft of the steam machine. An increase in the speed of the shaft causes a decrease in the pressure of the steam supplying the steam machine, which in turn causes a decrease in the speed of the shaft, thus opening the steam valve at the input and increasing the speed again. The phenomenon will lead to a fixed (stabilized) shaft speed with small fluctuations.

Clock

A typical analog clock (its face) hanging on many walls in a house (or mounted on many towers) looks like the one below:

Clock face

Possible construction of such a clock on the tower:

Example of a design reproducing a clock mechanism

The time measurement mechanism we use to explain the indication on the clock face, which is the basis for the construction of clocks, is expressed as a model in UML notation.

A model expressing the timing mechanism

Conceptual model.

We model domain knowledge as a Concept Dictionary, and this can be expressed graphically in the form of taxonomies and syntactic relationships. The application code architecture expressed graphically is its model, adding to fewer diagrams describing♥ for example, use case scenarios, is also part of this model. The whole, however, describes the mechanism for implementing functional requirements.

Below left conceptual model, he ne is, however, the mechanism for the implementation of functional requirements. On the right, the model (fragment) of the application architecture, supplemented with a sequence diagram, would be a model describing the mechanism of implementation of a specific functionality.

Summary

As you can see, sometimes it is easy to confuse the terms model and mechanism, but we can say that a model is a diagram depicting something, while a mechanism is an explanation of a phenomenon (how something is created how it works). A mechanism can be illustrated in the form of a model. If we aim for the model to be an idealization, then that’s it:

Modeling involves abstracting from the details and creating an idealization so as to focus on the essence of a thing. A good model only describes the mechanism.(Craver & Tabery, 2019).

Sources43790

Bertalanffy, L. (2003). General system theory: foundations, development, applications (Rev. ed., 14th paperback print). Braziller.

Craver, C. F. (2007). Explaining the brain: mechanisms and the mosaic unity of neuroscience. Clarendon Press.

Craver, C., & Tabery, J. (2019). Mechanisms in Science. In E. N. Zalta (Ed.), The Stanford Encyclopedia of Philosophy (Summer 2019). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/entries/science-mechanisms/

Frigg, R., & Hartmann, S. (2020). Models in Science. In E. N. Zalta (Ed.), The Stanford Encyclopedia of Philosophy (Spring 2020). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/spr2020/entries/models-science/

Weilkiens, T. (2007). Systems engineering with SysML/UML: Modeling, analysis, design (1. Aufl). Morgan Kaufmann OMG Press/Elsevier.