The UMDL project is a large-scale, multidisciplinary effort to design and build a flexible, scalable infrastructure for rendering library services in a digital networked environment. In order to meet these goals, we chose to implement the library as a collection of interacting agents, each specialized to perform a particular task and all of them acting in an artificial economy. These agents buy and sell goods/services from each other in an effort to make a profit. Since the UMDL is an open system, which will allow third-parties to build and integrate their own agents into the architecture, we treat all agents as purely selfish.