As far as open source geospatial databases go, PostGIS is the most commonly used spatial database. PostGIS is essentially a module on top of the well-known PostgreSQL relational database. Much of the power of PostGIS comes from the previously mentioned GEOS library. Like JTS, it also implements the OGC Simple Features specification for SQL. This combination of computational geometry ability in a geospatial context sets PostGIS in a category of its own.
PostGIS allows you to execute both attribute and spatial queries against a dataset. Recall the point from Chapter 2, Learning Geospatial Data, that a typical spatial dataset is comprised of multiple data types including geometry, attributes (one or more columns of data in a row), and ...
