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System
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is a part of the real world that is for some reason considered as a unit.
In a system, several phenomena are collected and combined.
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Phenomenon
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is an aspect in the real world that is essential for a system. Phenomena
are, for example, states of a system (e.g., the light intensity in a
room), events occurring in the real world (e.g., the switching on of a
light), objects (e.g., sensors and actuators), and individuals (e.g., a
facility manager of a building).
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Terms
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(e.g., words in natural language) are used to designate specific phenomena
of a system. They are a prerequisite for each conversation about real
world phenomena. We demand that there is a one--to--one relation between
phenomena and terms, i.e., for each phenomenon there is exactly one term
designating it, and each term designates exactly one phenomenon.
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Statements
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express relationships between several phenomena. Each statement is
constructed of the terms representing the considered phenomena. An example
of a statement is: If a room is occupied, then the light is on.
Here, a relation between the terms room, occupied,
light, and on is expressed.
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