MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
A Surface is a two-dimensional geometry. It
is a noninstantiable class. Its only instantiable subclass is
Polygon.
Surface
Properties
A Surface is defined as a
two-dimensional geometry.
The OpenGIS specification defines a simple
Surface as a geometry that consists of
a single “patch” that is associated with a
single exterior boundary and zero or more interior
boundaries.
The boundary of a simple Surface is the
set of closed curves corresponding to its exterior and
interior boundaries.