Re Joel's audience question on System Dynamics compared to System Design
Engineering:
The purpose of System Dynamics (SD) is enabling a correct choice of policy
or strategy in a complex setting; the purpose of System Design Engineering,
or equally commonly, just Systems Engineering (SE) is roughing out a
workable architecture and overall design for a complex device (or physical
system, or even man-machine system). For example, any air traffic control
system would have SE early in the design process.
Similarities
They both tend to use models at a higher level of aggregation, and
deliberately scope the system boundaries widely. Both are likely to start
out conceptual and end up mathematical (the ""phased approach""), and indeed
sometimes both have well-articulated modeling processes.
Differences
Different purposes create many differences. SD tends to be doing just one
model at a time, and always the continuous time, lumped parameter form we
know and love. SE may well use many models, each in a different form and
drawing on different disciplines for different parts of the system to be
designed. In terms of who does it and what they know, in SE technical
engineering knowledge is the main focus, and knowledge of the client
situation is an input to the process. In SD, the modeler is expected to be
extremely familiar with all the moving pieces in the client's world. That's
because a major task of the SD modeler is to represent that world. The SE
modeler/engineer's task is to only to design something that will work as
specified within that world.
Hope this is helpful. SD vs SE is one of those questions like SD vs
Dynamical Systems where general comparison is useful to a point, just to
know what goes on in other fields and perhaps extract isolated learning
points as part of some other endeavor. (For example, for those studying the
processes of model-building, a look at how SE is taught might be useful.
Just the ""phase gate"" process is a useful allusion.) But this isn't the
right forum for deep inquiries into SE. There are too many textbooks out
there for us to duplicate the content here.
cheers,
alan
Alan K. Graham, Ph.D.
Decision Science Practice
PA Consulting Group
Alan.Graham@PAConsulting.com
One Memorial Drive, Cambridge, Mass. 02142 USA