Information Technology Reference
In-Depth Information
Static versus Dynamic
Figure 2.1
The Static versus Dynamic curve.
Physical systems
are systems based on matter and energy.
Logical and
conceptual systems
consist of ideas, often referred to as models. A social
system based on morals and ethics may be considered an example of a
conceptual system. Scientists strive to create models of systems that allow
them to understand the systems, and predict what they will do in the
future or when certain things are changed.
. Determining the complete input-output
spectrum of a system by exhaustive measurement is practically impossible
to achieve. A system is considered linear if it is possible to use the outputs
to a small set of inputs to predict the output to any possible input. To
see whether a system is linear, one needs to test whether it obeys the
two basic characteristics (of linearity):
Linear
and
nonlinear systems
1.
Homogeneity.
As one increases the strength of a simple input to
a linear system, say double it, then one can predict that the output
function will also double. This is sometimes called the scalar rule
of linear systems.
2.
Aggregation.
Suppose one has an input X to a system, and one
measures the responses X
′
coming from it. Next, one presents a
second input Y that is a little different. The second input would
also generate a set of responses Y
′
that one measures. Then, one
presents the sum of the two inputs X + Y and observes the
responses. If the system is linear, then the measured response will
be X
′
+ Y
′
.
Systems that do not demonstrate these properties are nonlinear. Need-
less to say, the latter are definitely more complex to build, regulate, and
manage. For example, errors and bugs in a system pose problems that
are essentially nonlinear in nature; that is why there is so much stress on
