Z39.50 Resources - Z39.50 Document - Related Specifications - Object Identifiers
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This page provides information about Z39.50 resources, the maintenance of the Z39.50 standard, and the implementation and use of Z39.50: a client/server based protocol for searching and retrieving information from remote databases.

"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 (Contextual Query Language) -- standard query syntax for representing queries.

Both are based on Z39.50 semantics.