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Introduction
The concept of Qualitative System Dynamics (QSD) emerged in the 1980's, most prominently in the writings of Peter
Senge, Eric Wolstenholme, and Geoff Coyle, as a way of thinking about systems without the necessity of developing a quantitative
model as is required in conventional System Dynamics (SD). While the development and analsyis of qualitative models is fraught
with potential pitfalls, this author finds that the process of developing solid qualitative models stimulates probing dialogue
that greatly facilitates quickly sharing of insights and knowledge across a group. For highly uncertatin, complex, and controversial issues
that challenge traditional quantification, QSD methods can arguably provide insights much more quickly and efficiently
than traditional SD.
This section contains material, papers, and links related to QSD in the hope that the availability of this information
will spur others to build on this base and contriute to the development of even more robust qualitative methods.
A Definition for Qualitative System Dynamics
As the term Qualitative System Dynamics has been used rather casually in the past, it
seems appropriate to strive to define what QSD is and is not. I tend to think of QSD as a systemic approach to problems and
issues that reflects System Dynamics tenet that structure shapes the behavior of systems and facilitates discussion and investigation
of the issue or problem without requiring quantification of the relationships comprising the model. It should be noted that
QSD is not a method but, rather, encompasses a range of methods, logic, and heuristics, both qualitative and quantitative,
that can be brought to bear on qualitative systems models to provide insight into such issues as the nature of the system,
its leverage points, its likely behavior, and similar topics. (For clarity it is worth noting that the term System
Dynamics is used to represent both a specific method of modelling and a broader range
of activies associated with process of developing and interpreting SD models. In that context QSD is a flexible
process and not a singular method.)
It should also be noted that the methods comprising QSD are not necessarily unique to QSD but may be used in SD during
the development of a model or for communicating model logic.
Overview
The methods of QSD are especially appropriate when time or information constraits or uncertainty makes quantification
problematic but can also be used quite effectively in the conceptualization phases of building SD models. QSD typically begins
by developing causal logic using some form of causal map, causal loop diagram, or influence diagram (depending on the preferences
of the facilitator). (NOTE: This site will explore the differences in these forms of diagrams later but will use the term
influence diagram.) It is my experience that the development of the influence diagram will, in motivated groups, stimulate
deep and meaningful conversations and insights. Those of us who use QSD methods routinely find that this conversation alone
will often resolve groups dilemmas.
The methods of QSD go far beyond the drawing of diagrams by including a variety of methods for exploring the implications
of the group's mental models as captured and represented in the influence diagram. I am in the process of developing
a new web site to present more information about QSD and the methods for exploring mental models.
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