“…Every object have to be instantiated by a choice, and the combination of these choices leads to a specific formulation (model) of the problem, hence to different optimisation results. For instance, as stated by di Tollo and Roli [8], two main choices are possible for variables: continuous [15], [29], [31], [28] and integer [30], [21]. Choosing continuous variables is quite 'natural' and its representation is independent of the actual budget, while integer values (ranging between zero and the maximum available budget, or equal to the number of 'rounds') allow us to add constraints taking into account actual budget, minimum lots and to tackle other objective functions to better explain the problem at hand.…”