Information Technology Reference
In-Depth Information
while a quick sketch is “cold” because the viewer has to “fill in the blanks.”
Note that cold is not necessarily bad. It has its advantages because it
forces the viewer to get involved and engage some of their other senses
and faculties, such as thinking. Within software systems, when one selects
the media or channels for users to interact with — the screen, the report,
the manuals, training slides — one must keep in mind such concepts.
Wherever applicable, good interactions engage the users, not merely
inform them: low definition is not bad, just different.
System Dynamics
Jay Wright Forrester is a pioneer of computer engineering and the founder
of System Dynamics, which deals with the simulation of interactions
between objects in dynamic systems. System Dynamics is a strategy for
studying the world around us, something that all systems analysts do
when designing information systems. The central idea is for one to
understand how all entities in a system interact with each other; the
concept of “feedback” is the differentiating factor in the field of System
Dynamics.
Systems Dynamics is based on three broad and interrelated categories:
(1) systems thinking, (2) dynamic modeling, and (3) simulation and
modeling tools. This approach views system entities and people as inter-
acting through “feedback” loops, where a change in variable A affects
other variables B, C, or D over time, which in turn affects A, and so on.
One cannot study the link between A and B in isolation, and then study
the link between D and A, to predict how the system will behave. Only
the study of the entire system, as a feedback system, can lead to some
good predictions.
Any regulator (extending the Ashby example) can be used to explain
a feedback loop. Consider the volume controls of the audio system in a
car. At various points during the car ride, one may need to adjust the
volume: when one starts from home in a residential neighborhood (qui-
eter), then when one rolls up the windows as one enters the freeway,
and then, once again after exiting the freeway. It is a cascading feedback
loop, based on the surrounding ambient noise, leading one to regulate
the volume with smaller and smaller adjustments, until one reaches the
desired sound level.
This example can be used to illustrate the difference between systems
thinking and systems dynamics. Systems thinking would dictate that a
certain sound level, say 15 decibels, is good for residential areas and
another sound level, 30 decibels, is good for freeways. One can hard-
code such values in the software. One can make it more flexible by
