From the Publisher
Two Views of Interoperability
Interoperability is one of the underlying challenges of digital libraries. Collections and services are provided by many different organizations on many different computer systems. Information comes from many sources, is processed in many ways, and managed to very different quality standards. Some systems are state-of-the-art, others are nearing retirement. How can these heterogeneous components provide users with a single, coherent service?
This issue of D-Lib Magazine has two articles that look at very different aspects of this complex topic. The story by Barry Leiner describes an approach to interoperability at the level of computer systems. It is closely related to the November 1998 D-Lib article by Lagoze and Fielding. The emphasis is on identifying the system components, their functions, and the interfaces between them. Leiner's story concentrates on the overall architecture; the next level down would be to look at the specific formats, protocols, etc., that are required. Interoperability of computer systems has proved to be surprisingly difficult. Progress is slowly being made, however, and the work described in this paper is very promising.
The other article, by Thomas Baker, discusses a totally different aspect of interoperability, the semantics of metadata. His starting point is the subtleties of expressing the Dublin Core in many different languages; the article then broadens out into a discussion of how, in a fast moving world, there are inevitably pressures for variations and dialects of any standard that describes the content of digital library collections. His observations parallel experience from the pioneering interoperability work that developed the Z39.50 protocol. Completion of the technical standards was a notable achievement, but was not enough to achieve full interoperability. It was still necessary to address the semantics of the information that was exchanged. As a simple example, two systems might both accept a query for the field "author", but have widely differing interpretations of what constitutes an author. An underlying theme in Baker's article is the tension between standards that permit no variation and those that allow local flexibility and evolution with time. Interoperability is easier if no variations are allowed, but the real world is infinitely variable and gradual changes may be inevitable.
William Y. Arms
Publisher, D-Lib Magazine
Copyright (c) 1998 Corporation for National Research Initiatives
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