Basic Building Blocks

Data are stored within the STEMgis database as Features and Attributes to those features. Features can be aggregated into Feature Types, and Attributes can be grouped into Dictionaries. Both Feature Types and Dictionaries are user definable. These terms are described below:

STEMgis Features

Features are objects that have a spatial location, for example a road or field. The features do not need to be static in space or time. A feature may represent a dynamic object such as a body of water, a vehicle or an animal. The feature may also change it's physical appearance or definition through time, for example the boundary of a town changes over time, with the growth or decline of a population. A feature is stored/identified in the database by a unique text string. Each instance of a feature has an associated timestamp stored in the database and any instance or time period may be retrieved from the database.

STEMgis Feature Types

Features are grouped in the database as feature types, so for example a feature type might be towns and each feature belonging to this feature type would represent each individual town.

STEMgis Attributes

Attributes are values representing some phenomenon that relate to a feature. This may be a description or name of a feature or something that has been observed or measured at a feature. For instance, a feature of a beach may have attributes of name, visitors per year, water quality, tidal range, fish catches, rare species count, or aesthetic appeal. Each attribute value is related to a feature and again has a timestamp stored with it.

STEMgis Dictionaries

Attributes are grouped by user defined Dictionaries, which are simply a means of classifying the attributes in order to make searches easier. An example of a dictionary might be 'Chemical' which groups all attributes relating to chemical measurements (e.g. water quality) or 'Crime' which groups all attributes relating to crime statistics (e.g. number of robberies).