Replying to L02556, in which Peter mentioned the presence of loops, it's
worth while nothing that there is a nomenclature that describes model
structure. The structure of models can be described as:
o Hierarchical
o Cyclic
o Hybrid
The latter is a combination having hierarchical and cyclic components. By
systematically ignoring the underlying structure of models, and letting
structure be a byproduct of the kind of thinking that produces systems
dynamic models, the tail continues to wag the dog. Model logic is much
more vital than model dynamics. If the former is correct, the latter is
likely to be acceptable. If the former is wrong, thousands of xy plots
will not fix it.
-- JOHN WARFIELD Jwarfiel@gmu.edu