ISO 23950:1998

Overview - ISO 23950:1998 (Z39.50)

ISO 23950:1998 - titled Information and documentation - Information retrieval (Z39.50) - Application service definition and protocol specification - defines the Information Retrieval Application Service and specifies the corresponding Information Retrieval Application Protocol (Z39.50). Published 1998 (first edition), this standard documents connection-oriented, program-to-program communication for search and retrieval between information systems. It sets out the protocol control information, message exchange rules, and conformance requirements but does not prescribe internal implementation details or terminal/user-interface interactions.

Key topics and technical requirements

• Application service definition (Section 3): Model and characteristics of the Z39.50 information retrieval service - databases, result sets, and extended services. Defines core services such as Init, Search, Present, Segment, Delete, Access-control, Resource-control, Sort, Scan, Explain, Close.
• Protocol specification (Section 4): Abstract syntax and APDU definitions (ASN.1), protocol procedures, state tables, presentation and association control interactions, error handling, and extensibility rules.
• Conformance requirements: General and feature-specific conformance clauses for implementers, including required behaviors and message semantics.
• Message/record segmentation: Rules for segmentation and reassembly of large records and multi-part responses.
• Annexes and supporting artifacts: Object Identifiers (OIDs), attribute sets, record syntaxes, error diagnostics, extended result-set models, retrieval profiles and other reference formats useful for implementers.

Practical applications and who uses it

ISO 23950 (Z39.50) is targeted at organizations and systems that need standardized, interoperable search and retrieval between computer systems:

• Libraries and union catalogs - distributed searching of bibliographic databases and inter-library systems.
• Universities and research institutions - cross-system metadata queries and harvesting.
• Information services and digital repositories - programmatic discovery and retrieval of records across heterogeneous systems.
• Software vendors and system integrators - building gateways, federated search engines, or middleware that implement the Z39.50 protocol for automated interoperability.

Practical benefits include standardized query/retrieval semantics, support for result-set management, access control/resource reporting, and extensibility to support specialized services.

Related standards and notes

• Originated from ANSI/NISO Z39.50-1995 (adopted by ISO under fast-track).
• Protocol APDUs described using ASN.1 (Abstract Syntax Notation One).
• Implementers should review annexes in ISO 23950 for OIDs, record syntaxes, attribute sets, and profiles to ensure interoperability.

Keywords: ISO 23950, Z39.50, information retrieval protocol, information retrieval service, library interoperability, union catalog, search and retrieval, protocol specification, ASN.1, application service definition.