REPLY Models, Problems and Systems (SD7029)

[SDMAIL Douglas Franco]

Posted by  "Douglas Franco" <dfranco at cantv.net>

George and Jack insightful remarks concerning the modeling a problem or 
a system is quite useful. The Yogi Berra' advice, "If you do not know 
where are you going, you may not get there", comes into play. However, 
some models of a problem, may lead to modeling a system, when the model 
transcend the scope of the original problem. For instance, take the 
classical Inventory- Backlog model. As we all know, increasing 
inventories diminish delivery delay (increases customer quality), and 
recover market share. The dynamic of quality and productivity is 
endogenously implied. If you think of stocks as accumulation of 
resources(like machines, finished products, man-hours, money and even 
knowledge) and backlog as accumulation of customer needs, as Kim Warren 
has suggested, then Quality = Shipment/Backlog, and Productivity = 
Shipment/Inventory. , are faces of the same coin.  Total Quality 
Management, TQM, means satisfying customer needs, while Total 
Productivity Maintenance, TPM, means using inventories of resources. 
System Dynamics creates a new paradigm where two apparent contradictory 
management approaches are integrated in a powerful fancy, able to 
address thousands of problems at the same time, diminishing the waste of 
resources, by diminishing the waste of opportunities (shipment over 
backlog). The so called quality paradox, "worse before the better", 
becomes a small part of the graphical display of the results, as John 
Sterman has pointed out. In this case your are modeling a problem, but 
at the same time you are modeling a system, because, you are addressing 
simultaneously millions of problems who share the same fancy, firmly 
catch by our stock and flow hooks. The classical John Sterman paper 
about the Kuhn theories certainly illuminates this path which leaves 
behind problems and systems.  After all, DYNAMO was built to model a 
problem and ends up modeling many of them. Sometimes, the "root cause" 
is not only to represent managers' mental models, but to change them, as 
pointed out by Peter Senge (one of the dimensions of the fifth 
discipline: the personal growth). It takes purposes to model a system. 
The model is a means, but it can also be an end.

Douglas
Posted by  "Douglas Franco" <dfranco at cantv.net>
posting date  Sun, 11 May 2008 12:58:16 -0400