Formal manipulation of Forrester diagrams by graph grammars

A grammar that formally constructs the types of diagrams used in system dynamics is fully described. It belongs to the special kinds of grammars (attributed programmed graph grammars) that are applied to the construction of graphs and geometric figures. The flow diagrams used in system dynamics have been defined by `attributed graphs´ so that the approach could be applied. The grammar manipulates the graphs according to the requirements of the methodology. Basically, a method to achieve a formal program for interactive modeling upon any diagram, starting from the formal specification of the diagram, is presented