Abstract : Based on a variety of calibrations11. Bien que les catalogues de ressources numériques aient été introduits de bonne heure dans l'histoire de l'informatique  l'emploi généralisé du terme « bibliothèque numérique » remonte au début des années 90  ., we are now in the adolescence of digital libraries. Like any adolescence, there is reason for optimism and concern. The concern originates in part from the vexing problems that were addressed in early digital library workshops [8  D. E. Atkins, Report of the Santa Fe Planning Workshop on Distributed Knowledge Work Environments : Digital Libraries, 1997 ., 34  C. A. Lynch and H. Garcia-Molina, "Interoperability, Scaling, and the Digital Libraries Research Agenda," IITA Digital Libraries Workshop May 18-19 1995. href="http://www-diglib.stanford.edu/diglib/pub/reports/iita-dlw/main.html" class="spip_out">http://www-diglib.stanford.edu/diglib/pub/reports/iita-dlw/main.html>.] for which practical solutions have yet to be fully deployed. A few examples are illustrative. While Handles and DOIs88. . have been successfully deployed in the library and publishing communities, the goal of ubiquitous, persistent identifiers remains unmet. Widespread acceptance of Dublin Core and OAI-PMH appears to address initial goals for interoperable resource description. However, problems with the quality of metadata [58  J. Ward, "A Quantitative Analysis of Unqualified Dublin Core Metadata Element Set Usage within Data Providers Registered with the Open Archives Initiative," presented at Joint Conference on Digital Libraries, Houston, 2003.] compromise the utility of the standards. Federated identity middleware such as Shibboleth99. . begins to address authorization and authentication issues, but the underlying public key infrastructure that was seen as "essential to the emergence of digital libraries" [34  C. A. Lynch and H. Garcia-Molina, "Interoperability, Scaling, and the Digital Libraries Research Agenda," IITA Digital Libraries Workshop May 18-19 1995. href="http://www-diglib.stanford.edu/diglib/pub/reports/iita-dlw/main.html" class="spip_out">http://www-diglib.stanford.edu/diglib/pub/reports/iita-dlw/main.html>.] remains undeveloped. Despite efforts of the W3C's Semantic Web initiative [13  T. Berners-Lee, J. Hendler, and O. Lassila, "The Semantic Web," Scientific American, (50), May, 2001.], the holy grail of semantic interoperability [42  A. M. Ouksel and A. Sheth, "Semantic Interoperability in Global Information Systems," SIGMOD Record, 28 (1), 1999.] remains elusive. Finally, with increasing amounts of rich information born in digital form and stored in institutional repositories, we still lack standard, scalable techniques for fully preserving that information.