.. CGNS-How-to 
   Copyright (c) 2012 Marc Poinot, Onera The French Aerospace Lab

Data model
++++++++++

The :term:`CGNS/SIDS` is a **data model**. It describes the data you need
to define (mandatory or optional data) the semantics of it, the way you 
organize it and its relationships with the other data. This describes
a logical model of your application data.

Node and trees
==============

A CGNS is a tree. A tree is a node which has node has children. The top
node of a :term:`CGNS/SIDS` tree has the CGNSBase_t type.

Actual top node
===============

Node description
================


