Arc/info: a geo-relational model for spatial information

A data model for geographic information is described. Originally designed for thematic mapping and map analysis, the model lends itself to tabular data processing applications as well as automated cartography. The model is a combination of the topological model (to represent feature locations and topology) and the relational model (to represent feature attributes). A geographic information system is a spatial data base together with a set of spatial operators. Any spatial data base is derived from a model of geographic information. The usefulness of a geographic information system depends on having a data model appropriate for geoprocessing. This is particularly true when systems and data bases must serve a variety of purposes. The ARC/INFO data model was designed as the basis for a generalized geographic information system. The overall goal is for a practical data model with as much generality as possible. Specific goals are described in the following paragraphs. Generality. The data model should support data bases developed at a variety of scales and for a variety of purposes. It should be suitable for applications ranging from thematic mapping to land inventory to topographic mapping to urban base mapping. Simplicity. The data model should be as simple as possible and still meet its other goals. A simple data model is the key to implementing efficient and reliable geographic data bases and algorithms. Efficiency. The data model should provide the basic data structure for all geoprocessing functions. It should support efficient geoprocessing functions directly without requiring conversion of data to special "analysis" or "edit" formats. For example, a function such as polygon overlay should be done directly with the data model rather than requiring a grid cell copy of the data base. Functions which should be easily implemented using the data model are: bulk digitizing, high quality map graphics, polygon processes such as overlay and dissolve, non-graphic query and analysis, and network simulation. Adaptability. It should be possible for both the system user and system programmer to extend or adapt the data model for particular applications. This is especially true for 388