Update README.rst

Author: andamian

caom2utils/README.rst

@@ -5,3 +5,25 @@ caom2utils
     :target: https://pypi.python.org/pypi/caom2utils
 
 Utilities to facililate working with the CAOM2 model.
+
+Observation Validation
+---------------------
+
+Validates a CAOM2 element (Observation, Plane, Artifact, Part or Chunk) with respect to the attributes of the element and possibly all its sub-elements. Example of validations: attribute values, spherical geometry of planes, WCS of chuncks, etc.
+
+.. code:: python
+
+    from __future__ import (absolute_import, division, print_function,
+                    unicode_literals)
+    import sys
+    from caom2 import SimpleObservation
+    import caom2utils
+
+    obs = SimpleObservation('collection', 'observationID')
+
+    # change and update obs
+
+    try:
+        caom2utils.validate(obs)
+    except Exception:
+        print('My exception is not valid')