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Control in Terms of Statements and Commands

We know that there are two types of messages: descriptive, or statements, and imperative, or commands. The combination of the two creates a relation which is known as control. A system C controls system S if C receives from S statements and sends to S commands. Actually, this is a special case which is predominant in well-organized cybernetic systems. In the general case, the controlling system C also may directly alter the states of the controlled system S. The difference between direct intervention and sending a command is relative, though. It depends on the definition of the systems involved.

Example: you drive a car. Here C is you, and S is your environment: the car, the road, etc. You receive visual and audio messages from the environment and vary the position of the car's wheels to keep it on the road. This is a direct change of the state of the controlled system. But you can consider your steering wheel as an information channel, through which you send commands to the wheels proper.

Another example: remote control of a missile. Here you receive information from the missile's sensors and send commands to it. But if you do not wish, for some reason (although this is not really reasonable) to separate the information channel from the missile and consider them together as the controlled system S, then you exercize a direct intervention.

The relation between a language and metalanguage, or theory and metatheory, is also a control relation. Here S is the system that uses the language, and C is the system that uses metalanguage. We create metalanguage and metatheory in order to examine the works of the language and the theory. The flow of descriptive information is from the language S to the metalanguage C. The result of our examination of the language and theory is classification and construction of more sentences of the language and more theories - this is alteration of the state of the language S.

Copyright© 1991 Principia Cybernetica - Referencing this page

V. Turchin,

Sep 1991


Metasystem Transition Theory



Other Definitions of Control

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