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Z39.50 Protocol Overview
– Z39.50 is an international standard client-server, application layer communications protocol.
– It is used for searching and retrieving information from a database over a TCP/IP computer network.
– Developed and maintained by the Library of Congress.
– Covered by ANSI/NISO standard Z39.50 and ISO standard 23950.
– Widely used in library environments for interlibrary catalogue search and loan.

Search Syntax
– The protocol supports search, retrieval, sort, and browse functions.
– Search queries contain attributes from the bib-1 attribute set.
– The syntax allows for very complex queries.
– Functional complexity is limited by uneven implementations by developers and commercial vendors.
– Results for the same query can vary widely among different servers.

Modernization Efforts
– Z39.50 is a pre-Web technology.
– Modernization efforts include the ZING (Z39.50 International: Next Generation) projects.
– The successors to Z39.50 are the protocols SRU/SRW (Search/Retrieve via URL/Search/Retrieve Web service).
– SRU is REST-based and SRW uses SOAP.
– These projects have a lower barrier to entry for developers compared to the original Z39.50 protocol.

Firewall Information
– The registered network port number for Z39.50 is 210, but other port numbers are used worldwide.
– Dozens of other port numbers are used, such as 2100, 2200, 2210, 2213, 3520, or ports 2101 and higher for different databases.

Related Concepts and References
Wide area information server (WAIS)
– Dynix
– Koha
– OpenURL

Z39.50 (Wikipedia)

Z39.50 is an international standard client–server, application layer communications protocol for searching and retrieving information from a database over a TCP/IP computer network, developed and maintained by the Library of Congress. It is covered by ANSI/NISO standard Z39.50, and ISO standard 23950.

Z39.50 is widely used[as of?] in library environments, for interlibrary catalogue search and loan, often incorporated into integrated library systems and personal bibliographic reference software, and social media such as LibraryThing.

Work on the Z39.50 protocol began in the 1970s, and led to successive versions in 1988, 1992, 1995 and 2003. The Contextual Query Language (formerly called the Common Query Language) is based on Z39.50 semantics.

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