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Z39.50

December 15, 2023

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)[1] is based on Z39.50 semantics.

Search syntax edit

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 (named after Bath, England, where the working group 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[as of?]. The Bath Profile is maintained by Library and Archives Canada.

Modernization efforts edit

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/SRW (Search/Retrieve via URL/Search/Retrieve Web service), which drop the Z39.50 communications protocol (replacing it with HTTP) while still attempting to preserve the benefits of the query syntax. SRU is REST-based, and enables queries to be expressed in URL query strings; SRW uses SOAP. Both expect search results to be returned as XML.

These projects have a much lower barrier to entry for developers than the original Z39.50 protocol,[2] allowing the relatively small market for library software to benefit from the web service tools developed for much larger markets.

Alternatives include the following.[3]

Firewall information edit

The registered network port number 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).[4][5]

See also edit

References edit

  1. ^ CQL: the Contextual Query Language: Specifications SRU: Search/Retrieval via URL, Standards, Library of Congress
  2. ^ "The Z39.50 Information Retrieval Standard: Part I: A Strategic View of Its Past, Present and Future". www.dlib.org. Retrieved 2020-01-22.
  3. ^ "Linked Data in Libraries Metadata Retrieval and Harvesting".
  4. ^ "Library of Congress Z39.50 Firewall Information".
  5. ^ "IANA Port and Protocol Registry".

External links edit

  • Z39.50 Maintenance Agency
  • Z39.50 Standard Document (pdf)

December 15, 2023
this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, november, 2021, learn, when. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Z39 50 news newspapers books scholar JSTOR November 2021 Learn how and when to remove this template message 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 1 is based on Z39 50 semantics Contents 1 Search syntax 2 Modernization efforts 3 Firewall information 4 See also 5 References 6 External linksSearch syntax editThe 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 named after Bath England where the working group 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 as of The Bath Profile is maintained by Library and Archives Canada Modernization efforts editZ39 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 SRW Search Retrieve via URL Search Retrieve Web service which drop the Z39 50 communications protocol replacing it with HTTP while still attempting to preserve the benefits of the query syntax SRU is REST based and enables queries to be expressed in URL query strings SRW uses SOAP Both expect search results to be returned as XML These projects have a much lower barrier to entry for developers than the original Z39 50 protocol 2 allowing the relatively small market for library software to benefit from the web service tools developed for much larger markets Alternatives include the following 3 Open Archives Initiative Protocol for Metadata Harvesting OAI PMH SPARQLFirewall information editThe registered network port number 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 4 5 See also editWide area information server WAIS Dynix Koha OpenURL OpenSearchReferences edit CQL the Contextual Query Language Specifications SRU Search Retrieval via URL Standards Library of Congress The Z39 50 Information Retrieval Standard Part I A Strategic View of Its Past Present and Future www dlib org Retrieved 2020 01 22 Linked Data in Libraries Metadata Retrieval and Harvesting Library of Congress Z39 50 Firewall Information IANA Port and Protocol Registry External links editZ39 50 Maintenance Agency Z39 50 Standard Document pdf Retrieved from https en wikipedia org w index php title Z39 50 amp oldid 1168846380, wikipedia, wiki, book, books, library,

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