“So you guys say you do dynamic systems modeling but so far I've been reading about input and output variables, and from what I can tell your model structures are a-cyclical graphs…so how can you handle feedback?”.
We make a distinction between 2 classes of feedback. 1) strong 2) weak
This article needs to answer the above question.
From Design Approach…
Within a calculator, processes may be tightly bound in the sense the that coordination of the processes within the calculator is assured through feedback linkages among the processes represented by the calculator. When processes are tightly bound, controlling behaviour is effectively embodied in the physical flows among the processes. Feedback within a calculator is called strong feedback.
Calculators representing physical transformation processes are coordinated through a control space; feedback among calculators is not permitted except through this control space. Feedback through control space is called weak feedback; weak feedback loops involve user participation.
The computational procedure for systems with strong and weak feedbacks is as follows:
i) The values of control variables for each calculator are set for future time.
ii) Each calculator is executed independently over all time thereby resolving all the strong feedbacks.
iii) Values of the output variables are examined for possible tensions, possibly through views.
iv) The control variables are reset in order to resolve existing tensions through weak feedback.
