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SIGMA: A Knowledge-Based Simulation Tool Applied to Ecosystem ModelingThe need for better technology to facilitate building, sharing and reusing models is generally recognized within the ecosystem modeling community. The Scientists' Intelligent Graphical Modelling Assistant (SIGMA) creates an environment for model building, sharing and reuse which provides an alternative to more conventional approaches which too often yield poorly documented, awkwardly structured model code. The SIGMA interface presents the user a list of model quantities which can be selected for computation. Equations to calculate the model quantities may be chosen from an existing library of ecosystem modeling equations, or built using a specialized equation editor. Inputs for dim equations may be supplied by data or by calculation from other equations. Each variable and equation is expressed using ecological terminology and scientific units, and is documented with explanatory descriptions and optional literature citations. Automatic scientific unit conversion is supported and only physically-consistent equations are accepted by the system. The system uses knowledge-based semantic conditions to decide which equations in its library make sense to apply in a given situation, and supplies these to the user for selection. "Me equations and variables are graphically represented as a flow diagram which provides a complete summary of the model. Forest-BGC, a stand-level model that simulates photosynthesis and evapo-transpiration for conifer canopies, was originally implemented in Fortran and subsequenty re-implemented using SIGMA. The SIGMA version reproduces daily results and also provides a knowledge base which greatly facilitates inspection, modification and extension of Forest-BGC.
Document ID
20010060338
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Dungan, Jennifer L.
(NASA Ames Research Center Moffett Field, CA United States)
Keller, Richard
(NASA Ames Research Center Moffett Field, CA United States)
Lawless, James G.
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Environment Pollution
Meeting Information
Meeting: International Society for Ecological Modelling
Location: Knoxville, TN
Country: United States
Start Date: August 7, 1994
End Date: August 11, 1994
Funding Number(s)
PROJECT: RTOP 212-65-24
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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