Analysis of Causal Loop Diagrams
Posted: Thu Apr 01, 1999 1:16 pm
The paper "A Behavioral Approach to Feedback Loop Dominance Analysis"
will be published in the next issue of the System Dynamics Review. An
important distinction must made and kept clear between feedback loop
analysis, which the paper addresses, and causal loop diagrams, which the
original inquiry to this list addresses. Researchers as notable of Doerner
have suggested that topographic features of systems such as those mentioned
in the inquiry can suggest structural dominance. However I am not aware of
any rigorous or reliable method of analyzing systems for loop dominance
based only on causal loop diagrams. Causal loop diagrams do not describe
structure specificlly enough for quantitative dominance analysis. As an
example take any of the causal loop diagram descriptions of the system
archetypes and ask "When and under what conditions do each of these loops
dominate?". We typically answer "Well, it depends..." and then begin to
describe the structure and its relation to the behavior more specificlly.
My comments should not be interpreted as degrading the qualitative analysis
of loop dominance (in our program I give a lecture introducing the concept
of loop dominance using qualitative analysis before formal modeling skills
are developed), only that qualitative analysis is severly limited. As for
how we can use system behavior to analyze feedback loops more
rigorously...youll have to read the paper.
David Ford
System Dynamics Program
University of Bergen
From: "David N. Ford" <David.Ford@ifi.uib.no>
will be published in the next issue of the System Dynamics Review. An
important distinction must made and kept clear between feedback loop
analysis, which the paper addresses, and causal loop diagrams, which the
original inquiry to this list addresses. Researchers as notable of Doerner
have suggested that topographic features of systems such as those mentioned
in the inquiry can suggest structural dominance. However I am not aware of
any rigorous or reliable method of analyzing systems for loop dominance
based only on causal loop diagrams. Causal loop diagrams do not describe
structure specificlly enough for quantitative dominance analysis. As an
example take any of the causal loop diagram descriptions of the system
archetypes and ask "When and under what conditions do each of these loops
dominate?". We typically answer "Well, it depends..." and then begin to
describe the structure and its relation to the behavior more specificlly.
My comments should not be interpreted as degrading the qualitative analysis
of loop dominance (in our program I give a lecture introducing the concept
of loop dominance using qualitative analysis before formal modeling skills
are developed), only that qualitative analysis is severly limited. As for
how we can use system behavior to analyze feedback loops more
rigorously...youll have to read the paper.
David Ford
System Dynamics Program
University of Bergen
From: "David N. Ford" <David.Ford@ifi.uib.no>