BOX S.2
Characteristics of National-scale Applications

National-scale applications such as those discussed in this report—crisis management, digital libraries, electronic commerce, manufacturing, and health care—use computing and communications on a nationwide (even global) scale.1 "National scale" therefore implies the potential for large volumes of computation and communications, a large number and diversity of individuals and organizations, and the associated complexity. National-scale efforts such as crisis management are distributed across multiple locations, are often linked by networks, and make use of a variety of computing and communications resources. The people involved vary in expertise, ranging from scientists and engineers to citizens who may lack specialized technological knowledge. Because they operate in such a broad and diverse environment, computing and communications systems for these application areas must be able to survive and adapt to variety and rapid change in the needs of individuals and organizations for technologies.

The national-scale applications examined in the Computer Science and Telecommunication Board's three workshops have several elements in common:

  • Scale. National-scale applications raise qualitatively new challenges for computing and communications technologies because of the geographic distribution, extent, and diversity of requirements for processing, storage, and communication of information, as well as the number of interconnected end points-users, computers, and information sources and repositories.
  • Demand for dependability. As people come to rely increasingly on the computing and communications systems that serve national-scale applications, these systems begin to become part of the infrastructure society counts on, as the telephone system did early in the century. Consideration must be given to systems' survivability, security, fault tolerance, and graceful degradation (as opposed to catastrophic failure), among other issues. Systems must also respond to the rapid, continuing evolution of underlying technologies in a competitive marketplace.
  • Architectural diversity. Distributed ownership of systems among many organizations and individuals makes monolithic, rigidly defined architectures largely impractical.2 Common interests among parties in one application domain such as health care or banking may result in agreement on specific architectural elements, but these interests evolve, and so generality and flexibility are required. This requirement for generality and flexibility implies the need for common interconnection standards, as well as support for people to identify and integrate the resources available to them across multiple system architectures.
  • Heterogeneous interfaces and standards. National-scale applications are distinguished by an enormous degree of heterogeneity and decentralization in the interfaces and models of interaction among the systems that support them. Centralized control or widespread agreement on a set of protocols and functional interfaces is difficult to achieve.3 In designing systems to support broad national activities with many autonomous players, the determination of where, what, and how much to hold in common among system elements must be an ongoing process open to diverse—and competing—commercial implementations.4

    1  

    Although it is not the case that each instance of using these applications is necessarily distributed across the entire nation, one of their distinguishing characteristics is that a given use potentially may draw upon resources anywhere in the nation—in some cases, the world.

    2  

    Architectures are the underlying models of systems and how they relate to each other. Interfaces and standards generally embody a particular architecture; however, a standard may be used in more than one architecture, and an architecture may have more than one implementation.

    3  

    This is true even in a relatively centralized institutional context. For example, heterogeneity is quite evident in military systems, particularly when more than one service branch or national force is involved. In addition, because the Department of Defense and other users of large-scale systems are relying increasingly on available commercial technologies, the choice and definition of standards are becoming increasingly significant for them.

    4  

    The need for openness and evolution raises questions about how to achieve formal and informal standards and conventions on a national scale. The continuing need for standards to achieve interconnection and integration suggests the broad value of research that can clarify choices among alternative technologies while those technologies are being developed, can increase compatibility among technologies, or can generate new technologies that diminish the problems associated with heterogeneity.

ing activities in all of these areas. However, current state-of-the-art technology is not always adequate to meet existing and emerging demands. Society's dependence on information technology is not absolute; certainly, fire fighters can continue to put out fires without computerized maps, and doctors can write clinical reports with pen and paper. However, continued improvements in the quality, efficiency, accessibility, and dependability of nationally important industries and services are realizable through advances in information technology and their integration into the work practices of organizations and individuals.

Consequently, whether expressed as needs of society or as opportunities for researchers, unmet demands for improved capabilities in areas of broad national significance suggest many fruitful problems for research in and development of



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