Architectures

Information systems have moved from centralized systems to client-server environments. Our DLs therefore may follow that same path; scalability makes it almost obligatory.

Decentralized: Hyper-G

The Hyper-G system deals with scalability by restricting clients to generally connect to a local server. Local servers cache data, and access other Hyper-G servers as needed to get desired information. Local servers index and search full-text documents, and maintain their part of the distributed link database.

• Hyper-G supports collections as well as hypertext. There is a world root.
• Hyper-G provides local views or maps of links, supported by its distributed database that refers to anchors in any (even read-only) media form.

Centralized/Decentralized: NCSTRL

The Networked Computer Science Technical Report Library (NCSTRL) accomodates its Lite sites with a central server. Standard sites provide full service, supporting local search. The backup server (at Virginia Tech) handles searches for any server not available. Thus, NCSTRL supports a combination of centralized and distributed searching.

Related Works

• Intermediaries in libraries often reflect a centralized perspective.
• Oracles, representing the optimal situation, can function in groups in a distributed fashion.
• Handles and the related architecture developed from CNRI by Kahn and Wilensky, focuses on persistent naming of and access to digital objects. The handle system being managed by Arms will support a hierarchical naming authority mechanism, like that for ISBNs.