The optimisation device (1) comprises means (4) for inputting data, means (2) for defining, on the basis of input data, time windows of availability and efficiency, relative to resources in consideration, an element (6) for expressing a space of solutions, i.e. said time windows, as probabilities, generating time-continuous functions in compliance with said time windows, an element (8) for optimising the resource allocation plan from the solutions space expressed as probabilities in this way, and user means (11) for using an optimal allocation plan defined in this way.