The assignment of spectrum licenses through spectrum trading markets can be used as a mechanism to grant access to spectrum to those who value it most and can use it more efficiently. Although various methods for improved spectrum assignment have been proposed along the lines of Dynamic Spectrum Allocation (DSA) and others, several issues related to their implementation are still unsolved. Among them, how to deal with interference in a multi-provider environment and determining the elements and architectures for feasible implementations of spectrum trading markets. This paper analyzes several proposed kinds of trading interactions that may arise in a spectrum trading market and proposes a taxonomy of architectures that could be used to implement them. We also discuss the benefits and limitations of using a single or restricted set of wireless standards in the implementation of a spectrum trading infrastructure as a step towards Wireless Bandwidth Trading which is proposed as a possible path for a realizable instance of markets based on spectrum trading concepts.