Game objects are called entities.
King, Queen, Bishop, Knight, Rook and Pawn are the entities involved in the game of chess.
Active entities are called users : they can take decisions and issue orders concerning other entities.
TODO :add player / remove player
Relationships exist between all entities in the game, the resulting graph reflects the game state.
The entry point (or root) of the game state called the context contains a means to access all entities in a game by traversing the graph.
Different from game to game, this graph however contains basic usefull information directly available from the root :
TODO : must be able to produce Mementos as updates
TODO : interaction level in Data not to overload Visibility or Memento
TODO : Memento handles a collection of Data
TODO : Context = Data container
TODO : Memento must filter itself according to description provided by Visibility filter
