To be feasible, the concept of distributed and interoperable digital repositories - libraries or archives - depends strongly on an infrastructure of persistent identification, as well as on the reliability of the linkage scheme between distinct but related information resources, in order to assure to the user a continuous and convenient access to the digital contents. This paper describes the current state-of-the-art of persistent identification and linkage in the Internet, focusing on the interoperability of the open digital libraries. It contrasts various approaches to the issue and analyzes the most important schemes and their relationship: URN, PURL, DOI, CrossRef, Handle System and OpenURL.
digital libraries; persistent identifiers; URI; URN; PURL; DOI; CrossRef; Handle System; OpenURL