Elements of GIS

The GIS has been divided into four elements. They are hardware, software, data, and liveware.
DATA MODELS
Conversion of real world Geographical variation into discrete objects is done through data models. It represents the linkage between the real world domain of geographical data and computer representation of these features. Data models discussed here are for representing the spatial information.
Data models are of two types: Raster and Vector.
In raster type of representation of geographical data, a set of cells located by coordinate is used; each cell is independently addressed with the value of an attribute. Each cell contains a single value and every location corresponds to a cell. One set of cell and associated value is a layer. Raster models are simple with which spatial analysis is easier and faster. Raster data models require a huge volume of data to be stored, fitness of data be limited by cell size & output is less beautiful.

Vector data model uses line segments or points represented by their explicit x, y coordinates to identify locations. Discrete objects are formed by connecting line segments which area is defined by set of line segments. Vector data models require less storage space, outputs are appreciable, estimation of area/perimeter and editing is faster and convenient. Spatial analysis is difficult with respect to writing the software programme.