Z39.50 is an undeniably complex protocol designed for and used by a very specialized community. Like the traditional MARC record, it works well in the library context, but fails to forge connections between the library community and other information resources. In the perspective of the Internet, it isolates large amounts of data by presenting obstacles to access which most individuals and organizations are unable or unwilling to overcome. The development of the SRU protocol addresses many of these obstacles by implementing widely adopted standards for communication and data exchange. In addition, it offers a standardized query language that allows for the simplicity of search-engine style queries while providing the power and sophistication desired by advanced searchers.

On the other hand, SRU relies on organized metadata and a system of context sets which can be shared and mapped. It still borrows heavily on the attributes and structures of the Z39.50 protocol. This is most likely due to the continued use of SRU as an overlay on native Z39.50 interfaces. As more native SRU interfaces are deployed, the dependence on Z39.50 structures should weaken.

The aim of this project was to prepare for research involving the Explain operation and the factors involved in its use. The author's experience with the complexities of Z39.50 configuration made the availability of a detailed description of a service very exciting. After studying the protocol and its implementation in the YAZ proxy software, that excitement has been tempered by reality. While the OCLC Open SiteSearch Documentation interface demonstrates the feasibility of advanced use of the explain operation, the requirement that server administrators manually create and maintain the explain records results in a great disparity in the level of detail available from any specific service. The usefulness of a standard method of acquiring information about a service should not be denigrated, but it is only one step in the process. The explain operation will be most useful when native SRU interfaces to information resources are developed that generate the explain record directly from the service configuration without requiring additional actions on the part of the administrator. The author hopes that his future research into the factors surrounding the use of the explain operation and its relationship with organizational goals will assist in future developments of the protocol.

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