Persistent identifier distributed system for digital libraries

In this paper we present an Italian initiative, involving relevant research institutions and national libraries, aimed at implementing an NBN Persistent Identifiers (PI) infrastructure based on a novel hardware/software architecture. We describe a distributed and hierarchical approach for the management of an NBN namespace and illustrate assignment policies and identifier resolution strategies based on request forwarding mechanisms. Starting from the core motivations for the assignment of "persistent identifiers" to digital objects, we draw a state of art in PI technologies, standards and initiatives, and illustrate other NBN implementations. We then describe structure and goals of our initiative and illustrate the features already implemented in our system and the results of our testing activities. Finally, we draw some conclusions and point out the future directions of our work.