.. include-document:: org.gvsig.fmap.geom/reference-links
   :rest:

Primitive geometries must implement the Primitive_ interface. ISO19107_ describes the primitives as a geometric object that couldn't be descomposed in another primitive on the system. Solid_ is a primitive too, beacuse the diferent sides of a solid haven't got sense by themselves. 

The structure of primitives on gvSIG is shown in the next figure:

.. figure:: img/primitive.png
   :alt: TEXTO
   :align: center

Here there's an important difference between ISO19107_ and the model, because a Curve_ isn't composed by elements with smaller granularity than it, but is the own geometry which choose how to implement itself. In the Surface case is the same.