Federated digital library should enable heterogeneous data sources to be shared and allow users to access them easily. An integrated information retrieval mechanism for federated digital library based on mediator/wrapper was proposed. It used RDF as information exchange format, and implemented query translation and result integration. An FDL integrated information retrieval system using the mechanism was implemented. The designs of mediator and wrapper generator were introduced and the performance of the system was analyzed.

Metadata is one of the key technologies in the development of digital library. With emerging of various kinds of metadata, the interoperability of metadata will be a focus, and important aspect of interoperability of digital libraries. The article pointed out the reasons of producing metadata interoperability, then summarized complete resolutions of metadata interoperability, and put forward existed questions. Finally,the possibility of realizing metadata interoperability using grid technology was discussed.