Z39.50 is an

international standard international standard is a technical standard developed by one or more international standards organizations. International standards are available for consideration and use worldwide. The most prominent such organization is the International Org ...

client–server,

application layer An application layer is an abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network. An ''application layer'' abstraction is specified in both the Internet Protocol Su ...

communications protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchron ...

for searching and retrieving information from a

database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases sp ...

over a

TCP/IP The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the su ...

computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are m ...

, developed and maintained by the

Library of Congress The Library of Congress (LOC) is the research library that officially serves the United States Congress and is the '' de facto'' national library of the United States. It is the oldest federal cultural institution in the country. The libra ...

. It is covered by

ANSI The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The orga ...

/ NISO standard Z39.50, and ISO standard 23950. Z39.50 is widely used in

library A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vi ...

environments, for interlibrary catalogue search and loan, often incorporated into

integrated library system An integrated library system (ILS), also known as a library management system (LMS), is an enterprise resource planning system for a library, used to track items owned, orders made, bills paid, and patrons who have borrowed. An ILS usually is c ...

s and personal bibliographic reference software, and social media such as

LibraryThing LibraryThing is a social cataloging web application for storing and sharing book catalogs and various types of book metadata. It is used by authors, individuals, libraries, and publishers. Based in Portland, Maine, LibraryThing was developed ...

. 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.

Search syntax

The protocol supports search, retrieval, sort, and browse. Search queries contain attributes, typically from the bib-1 attribute set which defines six attributes to specify information searches on the server computer: use, relation, position, structure, truncation, completeness. The syntax of Z39.50 allows for very complex queries. In practice, the functional complexity is limited by the uneven implementations by developers and commercial vendors. The syntax of Z39.50 is abstracted from the underlying database structure. For example, if the client specifies an author search using attribute 1003, the server must determine how to map that search to the indexes it contains. This allows Z39.50 queries to be formulated without knowing anything about the target database, but it also means that results for the same query can vary widely among different servers. One server may have an author index and another may use its index of personal names, whether they are authors or not. A third may have no name index and fall back on its keyword index, and yet another may have no suitable index and return an error. An attempt to remedy the inconsistency is the

Bath Profile The Bath Profile is an international Z39.50 Specification for Library Applications and Resource Discovery. The Bath Profile is maintained by Library and Archives Canada. The syntax of Z39.50 is abstracted from the underlying database structure. F ...

(named after

Bath Bath may refer to: * Bathing, immersion in a fluid ** Bathtub, a large open container for water, in which a person may wash their body ** Public bathing, a public place where people bathe * Thermae, ancient Roman public bathing facilities Pla ...

, England, where the

working group A working group, or working party, is a group of experts working together to achieve specified goals. The groups are domain-specific and focus on discussion or activity around a specific subject area. The term can sometimes refer to an interdis ...

first met in 1999). This document rigidly specifies the search syntax to employ for common bibliographic searches, and the expected response of Bath-compliant servers. Implementation of the Bath Profile has been slow but is gradually improving the Z39.50 landscape. The Bath Profile is maintained by

Library and Archives Canada Library and Archives Canada (LAC; french: Bibliothèque et Archives Canada) is the federal institution, tasked with acquiring, preserving, and providing accessibility to the documentary heritage of Canada. The national archive and library is t ...

Modernization efforts

Z39.50 is a pre- Web technology, and various working groups are attempting to update it to fit better into the modern environment. These attempts fall under the designation ZING (Z39.50 International: Next Generation), and pursue various strategies. The successors to Z39.50 are the twin protocols

SRU SRU may refer to: Organizations * Salve Regina University, Newport, Rhode Island, US * Scottish Rugby Union * Shri Rawatpura Sarkar University, Chhattisgarh, India * Slippery Rock University of Pennsylvania, US * Sri Ramachandra University, Chenn ...

/ SRW (''Search/Retrieve via URL''/''Search/Retrieve Web service''), which drop the Z39.50 communications protocol (replacing it with

HTTP The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, w ...

) while still attempting to preserve the benefits of the query syntax. SRU is

REST Rest or REST may refer to: Relief from activity * Sleep ** Bed rest * Kneeling * Lying (position) * Sitting * Squatting position Structural support * Structural support ** Rest (cue sports) ** Armrest ** Headrest ** Footrest Arts and enter ...

-based, and enables queries to be expressed in

URL A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifi ...

query strings; SRW uses

SOAP Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are used a ...

. Both expect search results to be returned as

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. T ...

. These projects have a much lower barrier to entry for developers than the original Z39.50 protocol, allowing the relatively small market for library software to benefit from the web service tools developed for much larger markets. Alternatives include the following. * Open Archives Initiative

Protocol for Metadata Harvesting The Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) is a protocol developed for harvesting metadata descriptions of records in an archive so that services can be built using metadata from many archives. An implementation of OAI-P ...

(OAI-PMH) *

SPARQL SPARQL (pronounced " sparkle" , a recursive acronym for SPARQL Protocol and RDF Query Language) is an RDF query language—that is, a semantic query language for databases—able to retrieve and manipulate data stored in Resource Description ...

Firewall information

The registered internet IP port for Z39.50 is 210. Although the majority of servers use this port, there are dozens of other port numbers used worldwide by Z39.50 (e.g. 2100, 2200, 2210, 2213, 3520, or in one case, ports 2101 and higher for different databases).

References

External links

Z39.50 Maintenance AgencyZ39.50 Standard Document (pdf)
{{Authority control Application layer protocols Library automation Library of Congress Domain-specific knowledge representation languages

Search syntax

Modernization efforts

Firewall information

See also

References

External links