Within a geographic information system (GIS), not only is the data important, but also the structure of the data. The structure of the data determines how the data and relationships among data are to be stored, retrieved, and utilized. This structure and the environment in which it is organized, with particular reference to spatial data, is referred to as a spatial data architecture (SDA). Spatial database management systems utilize an SDA to implement their storage and management structures for spatial data. In fact, an SDA may involve multiple databases accessible via desktop, intranet, and Internet applications.