to accommodate the interdependencies—for example, to accommodate demands for service and access across architectures and standards that, as noted in Box S.2, are owned and controlled by multiple parties and are inevitably diverse. Indeed, one observer characterized it as a firm requirement that research on computing and communications in each application area take into account the others, noting, "You can't address one or two of them and let the others slide."

Digital libraries make more intensive demands for storage and bandwidth to manage and interchange image, audio, video, and numeric information than do activities with traditional high-performance computational requirements such as modeling and simulation. Digital libraries require substantial advances in software; information management technology and practices; and the ability to process, navigate, manage, and classify not only textual data but also multimedia, sensor feeds, and numeric data. Digital libraries also represent a primary focus of research in the scaling of very large, autonomously managed distributed systems. Central issues in the successful development of digital libraries encompass the identification, development, and adoption of appropriate standards, as well as fundamental questions about the definition of interoperability among systems and collections of information at various levels and the mechanisms that can be used to accomplish such interoperability.

Finally, it is important to recognize that digital libraries are not purely technological constructs; rather, they also encompass complex sociological, legal, and economic issues that include intellectual property rights management, public access to the scholarly and cultural record, preservation, and the characteristics of evolving systems of scholarly and mass communications in the networked information environment. The requirements for reflecting this broader context in software and network protocols are poorly understood but may generate substantial computational and infrastructure demands—for example, to examine intellectual property rights and ancillary evaluative or rating information associated with very large numbers of digital objects as part of query processing and result ranking. Design of technical approaches to support the social, legal, and economic framework of digital libraries that are sufficiently flexible to recognize and support reuse within a new framework is a challenging problem that itself has significant legal and economic dimensions. As resources that comprise digital libraries are reused in the crisis management environment, it may not be feasible, for example, to stop to negotiate a license agreement for access to a networked information resource that is needed urgently to respond to a crisis.

Digital libraries place extensive and challenging demands on infrastructure

Front Matter (R1-R14)

Overview and Summary (1-7)

Application Needs for Computing and Communications (8-54)

Technology: Research Problems Motivated by Application Needs (55-98)

Summary and Findings: Research for National-Scale Application (99-138)

Bibliography (139-142)

Appendixes (143-144)

A Workshop Series on High Performance Computing and Communications (145-155)

B Background--HPCCI and NII (156-157)

C Acronyms and Abbreviations (158-160)