Functionality
Quantum GIS provides integration with other open source GIS packages, including PostGIS, GRASS, and MapServer to give users extensive functionality.
Plugins, written in Python, extend the capabilities of QGIS. There are plugins to geocode using the Google Geocoding API, perform geoprocessing (fTools) similar to the standard tools found in ArcGIS, interface with PostgreSQL and MySQL databases, and use Mapnik as a map renderer.
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