System: What it is?

I came across awesome definition of System in "Thinking in Systems" book.  Thought of sharing :).

Definition from Thinking in Systems book:

"A system is an interconnected set of elements that is coherently organised in a way that achieves something. System must consists of three kinds of things:"

• Elements 
• Interconnections
• A function or purpose

Few examples: 

• Digestive System:
  • The elements of your digestive system include teeth, enzymes, stomach and intestines. 
  • They are interrelated through the physical flow of food 
  • The function of this system is to break down food into it's basic nutrients and to transfer those nutrients into blood stream ( Another System)
    
• Football Team:
  • The elements such as players, coach, field and ball
  • Its interconnections are the rules of the game, the coach's strategy, the players communication and laws of physics that govern the motions of ball and players.
  • The purpose of the team is to win games or have fun or get exercise or make million of dollars or all of above

How to identify a System (How to know whether you are looking at a system or just a bunch of stuff)

• Can you identify parts? ... and
• Do the parts affect each other? ... and 
• Do the parts together produce an effect that is different from the effect of each part on it's own? and perhaps 
• Does the effect, the behaviour over time, persist in a variety of circumstances?

Most difficult Part:

• It is easier to learn about a system's element than about it's interconnections:
  • Many of the interconnections in system operate through the flow of information. 
  • Information holds systems together and play a great role in determining how they operate?
• The least obvious part of the system, it's function or purpose, is often the most crucial determinant of the system's behaviour.
  • It dependants upon complexity of the system

"You think that because you understand "one" that you must therefore understand "two" because one and one make two. But you forgot that you must also understand"and" " - Sufi teaching story

Cheers!

Manisha