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The Defense Technical Information Center (DTIC), the Defense Advanced Research Projects Agency (DARPA), and CNRI are working to extend and transfer CNRI's Digital Object Architecture work into a prototype digital library implementation adapted to DTIC's needs and using DTIC data. This mutually beneficial project gives DTIC a potential framework in which to build network-based services and collections and gives CNRI a particularly valuable testbed in which to continue to develop and refine the relevant pieces of its Digital Object Architecture.
The basic approach is to combine both research level and commercial components to create a functional digital library, not to provide any level of production service, but to understand in a practical sense the new requirements and challenges facing an organization such as DTIC, e.g., description of information entities which exist primarily as digital objects. While the various components of this demonstration system are by nature designed to be distributed across networks, they will initially reside, for purposes of development and demonstration, on a single computer. The prototype system is available as the Defense Virtual Information Architecture at http://hdl.handle.net/100.10/DVIAProxy.
The primary components of the prototype are (1) a CNRI Repository in which the information objects are stored and from which they can be disseminated; (2) a CNRI Handle service which resolves names, or Handles, of the desired information objects into Repository or other locations; (3) a standard modern information retrieval or finding system which provides names of information objects in response to queries; and (4) a user interface in the form of a standard web browser which can be extended to understand the Handle System. See Figure 1 for a summary of this arrangement.
Components
Distributed Digital Object Repository Service
The first component of the prototype Defense Virtual Information Architecture is an implementation of the CNRI Distributed Digital Object Repository Service. The service is based on a Distributed Digital Object Repository Infrastructure designed at CNRI, in collaboration with Cornell University. It provides for the creation, access and management of distributed digital objects, and uses the handle service to locate its digital objects within the service. Digital objects provide a high degree of abstraction over their content, de-coupling their specific storage mechanism from their access methodology. Digital object access is referred to as a digital object dissemination. A dissemination can be thought of as a mechanism that provides a high level set of operations (or transformations) on the object's contents. Digital object disseminations enable clients to focus on the nature, behavior and characteristics of the data, rather than on its structure and/or bytes. Disseminations are inherently extensible, allowing new operations to be dynamically added to the service.
Handle Service
The second component of the prototype Defense Virtual Information Architecture is a current implementation of the CNRI Handle System. The Handle System provides rapid resolution of names, or identifiers, into current state information of network resources, e.g., location. It combines a single global and multiple local systems to allow for reliable management of names over the very long term. DTIC is a naming authority within this framework and has the ability to associate any names it creates with global location data.
Retrieval System
A retrieval or finding system forms the third major server component and provides the primary entré into the DVIA for end users. No basic information retrieval research is planned for the project and our goal here is simply to connect a modern retrieval system to demonstrate the Handle and Repository components as they would likely be used in DTIC systems and services. The current implementation uses VerityTM retrieval system.
User Interface
The framework for the user interface is a standard web browser, e.g., Netscape. Within this framework, we have built or obtained extensions and plug-ins as needed to work with the other components such as the multimedia data types.
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