The communication/interaction aspects are very relevant in the context of a SDSS also to enable sensitivity analysis studies. For this purpose the MCDA methods (SAW, TOPSIS, ELECTRE I), the RDBMS structure and the graphical interface to receive parameters and comparison of the alternatives in the criterion space have been developed fromscratch and incorporated into the ESRI ArcView®GIS platform. This was done to facilitate the user/systeminteraction and allowsMCPUIS to be utilized in other infrastructure systemplanning applications in other settings. The overall purpose of MCPUIS is to assist the DM in the assessment and selection of the investment option to be implemented. The DM supplied inputs (e.g., weights and threshold values, etc.) used by the MCDM techniques influence the results obtained using the different MCDA methods. Since these inputs parameters are “subjective” (i.e., they depend on the DM who may be not absolutely confident about the preferences he/she expresses in this setting) MCPUIS includes also a “sensitivity analysis” function to assess the stability (robustness) of the conclusions in face of distinct sets of input parameters.