The decision, at the end of the combination, consists in choosing, among all events , the event regarded as holding the true value that we seek. This decision can be made within two different frameworks.

• Either we make the assumption of a `` closed world '', in which case we assume that we know everything about the problem to be solved. The solution sought must lie in one of the events modelled, in general that having obtained the highest mass of evidence after combination. It is the simplest approach, but also less realistic.
  
  
• Or we make the assumption of an `` opened world ''. In this case, we allow the existence of non-modelled proposals, i.e. we have incomplete knowledge of the problem, and thus the solution sought can be among the modelled events, or can also be an unknown event in our model of the problem. This approach is of course the more realistic.