LIS 525 - Z39.50

Z39.50 is a communications protocol for retrieval of online bibliographic data. It is used on the Internet to search OPACs and sometimes to link OPACs into a single union OPAC.

Z39.50 specifies procedures and structures for a client to

It also specifies access and resource control, extended services, and a help facility. The protocol deals with communication between the client and server, but not interaction between the client and the end-user.

Z39.50 is a standard of the American National Standards Institute/ National Information Standards Organization, and an identical standard has been adopted by the International Standards Organization (ISO 23950).

Nearly all major North American library software vendors offer Z39.50 functionality as part of their suite of library products. A library may choose to acquire only a Z39.50 client application, only a Z39.50 server application, or both a client and a server application. Z39.50 server software tends to be much more expensive than client software. A Z39.50 client may be hosted on a Web server, providing a Web/Z39.50 gateway.

The client must have information about how to access each target (server): name of target, name of database, domain name, IP address, port number. Client software should include a list of common Z39.50 targets from which to choose and allow adding of other targets.

Historical Note: WAIS

WAIS (Wide-Area Information Servers) was an extension of Z39.50 in which specialized subject databases were created at multiple server locations, kept track of by a directory of servers at one location, and made accessible for searching by users with WAIS client programs. User could retrieve full texts of documents, not just catalog records.

WAIS has been essentially obsolete for years now, having been replaced by the Web. WAIS/Z39.50 traffic on NSFNet (the immediate predecessor of the commercial Internet in the U.S.) peaked in October, 1994.

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Last updated April 16, 2007.
This page maintained by Prof. Tim Craven
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Faculty of Information and Media Studies
University of Western Ontario,
London, Ontario
Canada, N6A 5B7