Cognitive Radio Networks (CRNs) are a key technology suggested to be part of 4G and beyond. The fundamental concept is to let Secondary Users (SUs) have temporal free access to spectrum bands not occupied by Primary Users (PUs). Since SUs are not allowed to cause harmful interference to PUs, SUs need to select the most available spectrum bands for access, also known as spectrum decision. In the paper, we suggest a middleware called Spectrum Decision Support System (SDSS) abstractly illustrated. The goal of SDSS is to combine the different decision methods together and to make intelligent band selection based upon partial characterizations of CRNs