• Some Commonly Used Phrases:
  • The systems needs to...
  • ... is a complex system...
• An Interesting/Troubling Observation:
  • Most people can't define the word "system"

System

A set of entities, their attributes, and the relationships between them.

Entities

The components of the system that are known/observed.

Attributes

The properties of the entities (i.e., the external manifestations of the way the objects are known or observed).

Relationships

The bonds that link objects and attributes

• A Definition:
  • Abstract (verb): To extract what is important
• Two Observations:
  • An object/concept can be conceptualized in an enormous number of ways
  • The level of detail (which is the inverse of the level of abstraction) is a defining feature of the system
• Example: A Car
• Low Detail - A source of emissions
• Medium Detail - A contributor to traffic congestion at an intersection
• High Detail - A mechanical motive device

We gauge the level of detail/abstraction by viewing the system under consideration in relation to:

Environment

The set of all other systems (also known as the context and the domain)

Subsystems

Parts of the whole which display a richness of interrelationships

Elements/Atoms

The smallest parts of the system (i.e., the black boxes)

• Physical Systems:
  • Can be "pointed to"
  • Include entities that exist in space and time
• Conceptual Systems:
  • All other systems

• Defined:
  • An unvarying (over space, and/or time, and/or some other dimension) description or summary of that system
• Specification:
  • All of the attributes (at an appropriate level of abstraction) of the entities that comprise the system