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 né 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., 14^th 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.