Location-allocation models are used in most cases on well-defined problems in which the environment is characterised with certainty. In those applications the geographical distribution of demand and the physical characteristics of the transportation network do not change over time. But locational planning problem environments are not static. In fact, most of their critical parameters are in flux, since they change as a result of demographic modifications (population growth or decline, migration), observed social and political trends, policy actions and the results of current socio-economic conditions and the development process. All these factors mainly affect the efficiency and robustness of proposed or applied solutions - strategies. In this paper, we describe a scenario-based approach of locational planning problems and we introduce MultiNet, a prototype information system, which aims both to support the approach and to assist the entire decision - making process. Finally, the system and the approach are utilised during a real world application; the location of new libraries in the region of Thrace, Greece.
