Building Infrastructures for Digital Libraries A. Bartelt 1 , D. Faensen 2 , L. Faulstich 2 , E. Schallehn 3 , C. Zirpins 1 Abstract Digital Libraries today are often monolithic systems. In the future, they will dissolve into collections of electronic services. The challenge will be to provide an infrastructure that supports the user in dealing with this multitude of services. Such an infrastructure should offer integrated access to the combined contents of multiple services, it should pro- vide active dissemination of new contents, and it needs to support the users in locating and combining the services most suitable to their needs. In the Global Info program Infrastructures for Digital Libraries components of such an infrastructure are being developed. The federated query service DEMETRIOS and the alerting service HERMES are both integration services that combine underlying services, i.e., heterogenous information sources. The GIBRALTAR portal provides a meta-service that supports the user in locating and applying various Digital Library services. 1 Introduction We expect that Digital Libraries of the future will be comprised of a large number of heteroge- neous services offered by various parties involved in the production, distribution, and archival of digital contents. For the user it becomes increasingly difficult to deal with a multitude of hetero- geneous services with different user interfaces and access mechanisms, and requiring separate registrations. Hence the goal is to facilitate the interaction of the user with a Digital Library consisting of a set of heterogeneous services offered by independent providers. In particular, the user needs support in three fields: First, users have to locate and combine appropriate Digital Library services, including trading and negotiation of service properties such as prices, licenses etc. Second, users want to search and query over multiple information sources. Third, users want to stay up-to-date on relevant content of the Digital Library. In this paper, we present three projects that address these issues. These projects constitute the program Infrastructures for Digital Libraries within the German Digital Library initiative Global Info [Glo01]. The DEMETRIOS federation service for bibliographical metadata is being developed at Uni- versity of Magdeburg. It supports the flexible integration of bibliographical data from multiple information sources of various types. The unified query service offered by DEMETRIOS can be utilized by other Digital Library services such as HERMES. The HERMES project at Free University Berlin has developed an alerting service for Digital Libraries [FFS 01]. Researchers who have entered their profile of interests into the HERMES 1 {bartelt,zirpins}@informatik.uni-hamburg.de 2 {faensen,faulstic}@inf.fu-berlin.de 3 eike@iti.cs.uni-magdeburg.de 1