Simple or non-simple geometries

The values of some geometry subtypes (linestrings, multipoints, and multilinestrings) are either simple or non-simple. A geometry is simple if it obeys all the topological rules imposed on its subtype and non-simple if it doesn't.

A linestring is simple if it does not intersect its interior. A multipoint is simple if none of its elements occupy the same coordinate space. Points, surfaces, multisurfaces, and empty geometries are always simple.