Interoperability of functions in environmental models - a case study in hydrological modeling

The monolithic structure of process-based environmental models has become a major obstacle in dealing with complex environmental problems. Interoperability is the inevitable direction for future generations of models. This article discusses the identification of equation functions for interoperable environmental models. These equations represent environmental processes that are implemented as algorithms in the models. The identification of common equations in existing models helps develop equation components that can be assembled to form customized models. In the context of a semantic reference system, formal concept analysis is used to decompose existing models, extract the common equations embedded in them, and organize these equations in a hierarchy of a concept lattice. The hierarchical structure of the lattice helps identify the relationships between equations across different levels and within the same level. Insights drawn from the concept lattice provide valuable information for the framework design of customized models and the adaptation of algorithms from existing models for the development of equation components. An important hydrological process, surface runoff, is used as an example of an environmental process to illustrate the analysis. To support the discussion, a customized surface runoff model is built using three components extracted from several existing hydrological models to predict surface runoff of a watershed.