Information Technology Reference
In-Depth Information
Fig. 15.3
A taxonomy of cybernetic devices.
To p l e f t
: a fixed computational device.
Top right
:
a fixed robotic device.
Bottom left
: an adaptive robotic device that modifies its computational in-
put-output mapping contingent on its evaluated performance.
Bottom right
: a robotic device that
adaptively constructs its sensing, effecting, and computational hardware contingent on its evaluated
performance
emulating the behaviour of a formal system. It is as if one were to perform a cal-
culation, say of the thousandth digit of
π
, but midway in the calculation the result
depends partially on fine variations of the temperature in the room. Only rarely will
two such procedures produce the same result, and one now has a process that is the
antithesis of a formal procedure. When coupled this way such devices, in formal
terms, become machines with inputs from oracles, where the internal workings of
the oracle are left ill-defined (Turing
1939
). Coupling a deterministic finite state au-
tomaton to a sensor that makes measurements converts the composite device to a
finite state oracle machine, a decidedly different kind of beast (Hodges
2008
).
Adding measurements are useful for some purposes, such as responding appro-
priately to changes in an external environment, but highly detrimental to others,
such as performing reliable, determinate calculations, where one is interested in the
purely logical consequences of the application of specified rules on initial inputs.
For these reasons, our physical computing devices have been designed and built, as
much as possible, to operate in a manner that is independent of their environs.
Accordingly, one can add fixed sensors and effectors to purely computational
devices to create robotic devices (Fig.
15.3
, top right) that have behaviours that are
qualitatively different from those of formal systems. These kinds of systems, which
include animals and artificial robots, have specific perception and action linkages to
the external world, thereby endowing their internal states with external semantics.
