Update pig-006.md
@@ -109,4 +109,6 @@ For the `Observation` class, the current `DataStoreObservation` can be a prototy
In a second step we want to generalize the *data store* classes and implement the `DataStoreXML` and `DataStoreInMemory` classes.
+### Proposed class diagram
+
![Proposed class diagram](https://github.com/dcfidalgo/gammapy/blob/pig-006/docs/development/pigs/pig6_class_diagram.png)
