Z39.50 is an

international standard An 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 O ...

client–server,

application layer An application layer is an abstraction layer that specifies the shared communication 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 variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...

for searching and retrieving information from a

database In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...

over a

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

computer network A computer network is a collection of communicating computers and other devices, such as printers and smart phones. In order to communicate, the computers and devices must be connected by wired media like copper cables, optical fibers, or b ...

, developed and maintained by the

Library of Congress The Library of Congress (LOC) is a research library in Washington, D.C., serving as the library and research service for the United States Congress and the ''de facto'' national library of the United States. It also administers Copyright law o ...

. It is covered by

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

NISO The National Information Standards Organization (NISO; ) is a United States non-profit standards organization that develops, maintains and publishes technical standards related to publishing, bibliographic and library applications. It was found ...

standard Z39.50, and

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

standard 23950. Z39.50 is widely used in

library A library is a collection of Book, books, and possibly other Document, materials and Media (communication), media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or electron ...

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 is usually ...

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 b ...

. 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 Contextual Query Language (CQL), previously known as Common Query Language, is a formal language for representing queries to information retrieval systems such as search engines, bibliographic catalogs and museum collection information. Based on t ...

(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 Plac ...

, England, where the

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

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; ) is the federal institution tasked with acquiring, preserving, and providing accessibility to the documentary heritage of Canada. The national archive and library is the 16th largest library in the world. T ...

Modernization efforts

Z39.50 is a pre-

Web Web most often refers to: * Spider web, a silken structure created by the animal * World Wide Web or the Web, an Internet-based hypertext system Web, WEB, or the Web may also refer to: Computing * WEB, a literate programming system created by ...

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 HTTP (Hypertext Transfer Protocol) 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, wher ...

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

REST REST (Representational State Transfer) is a software architectural style that was created to describe the design and guide the development of the architecture for the World Wide Web. REST defines a set of constraints for how the architecture of ...

-based, and enables queries to be expressed in

URL A uniform resource locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identi ...

query strings; SRW uses

SOAP Soap is a salt (chemistry), salt of a fatty acid (sometimes other carboxylic acids) used for cleaning and lubricating products as well as other applications. In a domestic setting, soaps, specifically "toilet soaps", are surfactants usually u ...

. 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 data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...

. 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 A web service (WS) is either: * a service offered by an electronic device to another electronic device, communicating with each other via the Internet, or * a server running on a computer device, listening for requests at a particular port over a n ...

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- ...

(OAI-PMH) *

SPARQL SPARQL (pronounced ":wikt:sparkle, sparkle", a recursive acronym for SPARQL Protocol and RDF Query Language) is an RDF query language—that is, a Semantic Query, semantic query language for databases—able to retrieve and manipulate data sto ...

Firewall information

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).

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