1. an abstract representation of objects and events from the real world for the purpose of simulating a process, predicting an outcome, or characterizing a phenomenon —note types of models include mental models (a set of rules that may or may not lend themselves to formalization and transfer among experts), quantitative models (which capture relationships as mathematical equations), data models (which capture relationships among data, often diagramatically), spatial models (e.g., GIS, paper maps), physical models (e.g., fuel beds in wind tunnels, sand and water hydrologic models), and financial models (which emphasize the timing and magnitudes of costs and benfits) 2. GIS data representation of reality, e.g., spatial data models, include the arc-node, georelational model, rasters or grids, polygon, and TINs —note the terms modeling and analysis are often used interchangeably, although the former is more limited in scope This definition last updated 10/26/2008