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This page provides links to information about Z39.50 resources and about the development and maintenance of Z39.50 (existing as well as future versions) and the implementation and use of the Z39.50 protocol.

"Z39.50" refers to the International Standard, ISO 23950: "Information Retrieval (Z39.50): Application Service Definition and Protocol Specification", and to ANSI/NISO Z39.50. The Library of Congress is the Maintenance Agency and Registration Authority for both standards, which are technically identical (though with minor editorial differences).

See also:
SRU (Search/Retrieve via URL) -- a standard search protocol for Internet search queries.
CQL (Common Query Language) -- standard query syntax for representing queries.

They are based on Z39.50 semantics.

The standard specifies a client/server-based protocol for searching and retrieving information from remote databases.

Z39.50 Proposals

Z39.50 Maintenance Agency: z3950@loc.gov
Maintenance Agency Procedures