Transformation of Qualitative Dynamic Models - Application in Hydro-Ecology

Hydro-ecological systems comprise complex interaction among physical, chemical, and biological processes. Compositional modeling, i. e. creating a system's behavior model by aggregating models of its constituents, is crucial for making the modeling task feasible. However, the composed model is often too fine-grained for a particular task, for instance, in containing too many irrelevant intermediate variables or obscuring the basic interdependencies. For this reason, the model may have to be transformed and simplified. The paper presents a graph-oriented representation for dynamic systems closely related to existing process languages, and a set of syntactic operators that transform such a model while preserving certain properties of the model. The formalism is motivated and illustrated by an example taken from our work on modeling hydro-ecological systems, but we also demonstrate its utility for technical applications.