REPLY Models, Problems and Systems (SD7004)

[SDMAIL Bill Braun]

Posted by  Bill Braun <bbraun at hlthsys.com>

John Weldon asks if the SD problem focus rule is deficient, citing some 
examples of systemic models that delivered results. Kim Warren, in 
response to Weldon, notes, "I too have been puzzled by where this mantra 
of 'model the problem, not the system' came from and what its 
justification might be."

The seminal works in SD are all systemic in scope - the problem focus 
for Industrial Dynamics was the "success of the enterprise" (p 13), for 
Urban Dynamics it was "urban decay and revival" (p ix), and for World 
Dynamics the "behavior of the world system" (p ix). All broad and still 
problem focused.

I suspect that the admonition on modeling the problem is not meant to 
limit scope, but to remind us to model only what is necessary to produce 
reference mode behavior. It may be that "only what is necessary" is 
complex and far reaching.

A quick review of SDR papers on group model building reveals they all 
stress diversity of mental models. A number of books off the shelf all 
consistently point to variables, reference mode, and dynamic hypothesis 
for model construction. (I rely on a paper by Jim Hines, with minor 
variations.)

While reference modes (and the dynamic hypothesis) may change as 
additional mental models are brought into the conversation (i.e., the 
iterative nature of conceptualization), would they not by themselves 
define the scope of the model, whether that turns out to be "problem" or 
"systemic" in nature? The model boundaries are less a matter of a 
declaration early in the process and more a matter of what emerges from 
the reference modes.

Bill Braun
Posted by  Bill Braun <bbraun at hlthsys.com>
posting date  Fri, 09 May 2008 05:33:01 -0400