Qualitative modeling can help us understand the effects of multiple stresses on plant physiological processes. For many systems, it is not practical to collect and correlate empirical data for all combinations of plant/environments and their biotic and abiotic stressors. It is often sufficient to predict qualitative dynamics effects (as opposed to system quantities), especially for research purposes.
In this effort, an object-oriented application framework (APF) was developed for the qualitative modeling of natural-resources systems. An application framework is a collection of reusable object classes that provide basic functionality for a class of applications. The user creates subclasses that inherit this functionality, and that are specific to his or her application. Smalltalk, an object-oriented programming (OOP) language, was chosen for the APF.
The modeling methodology is based on research published by the second author. In the methodology, parameters represent variables of interest in the model system. In a plant growth simulation, for example, Growth and Photosynthesis might be represented by parameters. The magnitude of a parameter is represented by its quantity, a fuzzy number, and the effects of changes in parameters upon one another are simulated over time by fuzzy arithmetic. The values of the changes in parameters and their quantities are then translated into linguistic values such (e.g., "low", "moderately increasing", etc.) via the mechanisms of fuzzy logic.
The APF includes classes providing all the functionality for constructing application-specific fuzzy simulation, including FuzzyNumber, Parameter, FuzzySimulation and Timer. Also included are data-structures such as KeyValueList and AssociationList, and modifications to Smalltalk to smoothly integrate fuzzy arithmetic for non-fuzzy values. The framework runs under Microsoft Windows 3.1, and includes a graphical user interface. In this paper, we present the APF along with an example simulation of plant physiology.
Key words: qualitative simulation, fuzzy plant physiology.
Correspondence: Richard Olson, USDA-ARS, P.O. Box 5367, Mississippi State, MS 39762, USA
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