different viewpoint of a situation. SSM provides the systems thinking
necessary to help those involved define existing situations, identify the
changes desired, and take actions to improve.
Literature
Models help communicate concepts, understand interrelations, and
develop new insights (Wilson and Morren, 1990, p. 75). Physical mod-
els of an object or system are typically made to change the scale, rep-
resent conditions at a point of time, or simulate output for varying
conditions. Models of airplanes, for example, are used in wind tunnels
to study aerodynamics. Photographs represent a person’s appearance at
the moment the shutter is snapped. Designers often use drawings to stim-
ulate changes while developing innovative solutions.
Symbolic models make it possible to communicate ideas and con-
cepts about how things function. Simple x-y plots help to visualize
trends, data variability, and other statistical information. Mathematical
equations are symbolic models ranging from simple linear expressions
to complex representations of nonlinear, time-varying, stochastic sys-
tems. Schematic diagrams are also symbolic models commonly used for
electrical circuits, distribution of materials, organization responsibilities,
and other visual displays. A key advantage of diagrams is the ability of
users to process information in parallel rather than in a series as when
reading words.
Visual models for showing systems are based on drawing a bound-
ary to show those components inside the boundary that constitute the
system and those outside the boundary (Wilson, 1990). The following
is a summary of the properties listed by Wilson and Morren (1990,
p. 190) as required for a system to qualify as a system:
- Has an ongoing purpose.
- Has a measure of performance.
- Has a process of decision making and resource allocation.
- Has components (subsystems) that exhibit all the properties of a
system. - Has components that interact.
- Exists within a wider environment with which it interacts.
- Can be distinguished from the environment in which it exists by a
boundary that represents the interface between the system and its en-
vironment.