System properties: an introduction

Copyright 2016 Graham Berrisford.

One of about 300 papers at http://avancier.website. Last updated 10/01/2017 13:45

 

The universe and human existence are ever-unfolding processes in which we perceive discrete entities.

Some entities are called systems, but what makes an entity a system?

System operators don't have to understand the properties that define what a system is.

Just as a footballer doesn't have to understand how kicking a football could be described using aerodynamics theory.

But systems describers have to understand the properties that define what a system is.

Because if it can't be described as having the properties of a system, then it ain't a system, and it can’t be designed as a system.

Contents

Generalising from dictionary definitions. 1

Generalising about activity systems. 1

Sequences in system operation and in system design. 2

More systems properties. 2

 

Generalising from dictionary definitions

This table shows system features found in the two popular internet sources and three dictionaries (A, B and C)

Feature

Google

A

B

C

W’pedia

Meaning

Wholeness (or holism)

yes

yes

yes

yes

yes

parts cooperate in processes to act as a whole (rather than act in isolation).

Interdependent or cooperating components

yes

yes

yes

yes

yes

all parts are related directly or indirectly

Orderly or rule-bound behaviour

yes

yes

 

yes

yes

system processes are constrained, bound by the rules of physics, chemistry or man.

System boundary (or encapsulation)  

 

 

yes

yes

yes

things inside the system are separable from things outside the system.

Input/output exchange across boundary

 

 

yes

yes

yes

the system is open to and interacts with its environment

 

The systems of interest here are characterised by orderly or rule-bound behavior.

All such systems are islands of stability carved by humans or by evolution out of the ever-unfolding processes of the universe.

Every system has a limited life time; some change in discrete evolutionary steps from one generation to the next.

 

A system classification based on system properties above

This table maps system properties, drawn from dictionaries above, to a classification of system types.

Most of this work is about dynamic activity systems.

A system classification

Discrete entity

Entity that cannot be described as a system

Entity that is disorganised

Entity that (organised or not) cannot be described because it is continually changing

Entity that can be described as a system

System boundary

Wholeness

Cooperating components

Static system: a passive structure with no behaviour

Dynamic or activity system

Orderly or rule-bound behaviour

Naturally-evolved system

does not depend on description by actors

Inorganic natural machine (solar system)

Organic entity (tree or cat)

Natural social organisation

Designed system

depends on description by actors

(symphony, business or software system)

Closed system (as in System Dynamics)

Open system

Input/output exchange across boundary

 

Generalising from system theory sources

To call something a system without reference to testable considerations is to say little.

Churchman says "a thing is what it does" and outlines five considerations for a system.

·         the total system objectives and performance measures;

·         the system’s environment: the fixed constraints;

·         the resources of the system;

·         the components of the system, their activities, goals and measures of performance; and,

·         the management of the system.

 

But those are considerations for business organisations in particular.

The properties of systems were generalised by system theorists before and without consideration of business or software systems .

“The same concepts and principles of organization underlie the different disciplines (physics, biology, technology, sociology, etc.), providing a basis for their unification.” Principia Cybernetica

 

Principia Cybernetica says this of a system:

real systems are open to, and interact with, their environments….”

“Systems theory focuses on the arrangement of and relations between the parts which connect them into a whole.”

“Systems concepts include: system-environment boundary, input, output, process, state, hierarchy, goal-directedness, and information.” Principia Cybernetica (Web)

 

This table presents an analysis of concepts from five sources.

Generic structure

Principia Cybernetica

Boulding’s social system

Checkland’s Soft System

Maturana’s biological entity

Wikipedia’s “system” entry

Active structure

Interrelated parts/actors

Individuals perform roles in

Components interact coherently in

Interacting components are transformed and destroyed

Related components perform

Behavior

interact in processes to meet goals by

repeatable processes according to

activities to meet a purpose by

by a network of processes that form

processes that transform

State

maintaining system state and

remembered mental images, and

maintaining their integrity and

a machine, a concrete unity

 

I/O Boundary

sending/receiving information

exchange messages

sending/receiving inputs and outputs

 

inputs into outputs (material, energy or data)

Environment

to/from each other and external actors

 

to/from each other and external actors

in space

 

 

To generalise from the above analysis, a set of basic considerations would be:

·         parts/actors (active structure) interact by

·         playing roles in processes (behaviors) to meet goals by

·         maintaining system state and

·         sending/receiving information to/from each other and

·         to/from the external environment (across the I/O boundary)

·         using resources.

 

Sequences in system operation and in system design

At the risk of being simplistic, a business system operation works as in the left hand column of the table below.

And a natural system design method is to (roughly) reverse the run-time sequence - as in the right hand column of the table below.

After implementation, run-time actors should behave in reality as the design-time description directs them to behave.

A sequence in run-time reality

A sequence for design-time description

1

Input events/messages trigger…

Goals - desired outcomes

2

Actors to perform activities in rule-driven…

Outputs to enable the goals to be met

3

Processes, that consume inputs and use resources to make…

Inputs and resources needed to make the outputs

4

Outputs, and so enable the consumers of those outputs to realise the…

Processes/rules to transform inputs into outputs using resources

5

Goals, the desired outcomes, of the system sponsors.

Actors to perform the processes

6

Resources needed by actors to do the work

 

More systems properties

System properties discussed in the literature and on web site include:

·         Encapsulation of structure and behaviour

·         Information feedback loops

·         The primacy of behaviour

·         Determinism and hysteresis

·         Change: adaptation and evolution  

·         Holism and emergent properties

·         Complexity

·         Goal-directedness

·         Chaos and non-linear behaviour

·         Unpredictability

 

 

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