Each element of a map layer is given a unique ID number. These unique ID numbers tie into a database management system. This allows for the addition of attributes describing the cartographic data.
For example, Wilson has a tax parcel layer that contains cartographic information depicting the boundaries of each parcel in the county and for each parcel there are approximately 75 attributes describing the parcel. This allows a user to be able to sit at a GIS terminal, visually select an area of interest, bring any layers of interest onto the screen, and select and list information about any of these layers.