relevant wikipedia pages: - http://en.wikipedia.org/wiki/Immutable_object http://en.wikipedia.org/wiki/Immutable_object - http://en.wikipedia.org/wiki/Persiste

relevant wikipedia pages: - http://en.wikipedia.org/wiki/Immutable_object http://en.wikipedia.org/wiki/Immutable_object - http://en.wikipedia.org/wiki/Persistent_data_structure http://en.wikipedia.org/wiki/Persistent_data_structure