The current library bibliographic infrastructure was constructed in the early days of computers – before the Web, XML, and a variety of other technological advances that now offer new opportunities. General requirements of a modern metadata infrastructure for libraries are identified, including such qualities as versatility, extensibility, granularity, and openness. A new kind of metadata infrastructure is then proposed that exhibits at least some of those qualities. Some key challenges that must be overcome to implement a change of this magnitude are identified.