LIS 525 - Z39.50
Z39.50 is a communications protocol
for retrieval of online bibliographic data.
It is used on the Internet to search OPACs
and sometimes to link OPACs into a single union OPAC.
Z39.50 specifies procedures and structures for a client to
It also specifies access and resource control, extended
and a help facility.
The protocol deals with communication between the client and
but not interaction between the client and the end-user.
- search a database provided by a server,
- retrieve database records,
- scan a term list, and
- sort a result set.
Z39.50 is a standard
of the American National Standards Institute/
National Information Standards Organization,
and an identical standard
has been adopted by the International Standards Organization
Nearly all major North American library software vendors
offer Z39.50 functionality as part of their suite of library
A library may choose to acquire only a Z39.50 client
only a Z39.50 server application,
or both a client and a server application.
Z39.50 server software tends to be much more expensive than
A Z39.50 client may be hosted on a Web server,
providing a Web/Z39.50 gateway.
The client must have information about how to access each target
name of target, name of database, domain name, IP address, port
Client software should include a list of common Z39.50 targets
from which to choose
and allow adding of other targets.
Historical Note: WAIS
WAIS (Wide-Area Information Servers)
was an extension of Z39.50
in which specialized subject databases were created
at multiple server locations,
kept track of by a directory of servers at one location,
and made accessible for searching by users with WAIS client
User could retrieve full texts of documents,
not just catalog records.
WAIS has been essentially obsolete for years now,
having been replaced by the Web.
WAIS/Z39.50 traffic on NSFNet
(the immediate predecessor of the commercial Internet
in the U.S.)
peaked in October, 1994.
For More Information
- Abbas, J.; Antonelli, M.; Gilman, M.; Hight, P.; Hoski, V.; Kearns, J.;
Lepchenske, T.; Peet, M.; Pullin, M.; Stults, A. 1999.
An Overview of Z39.50,
Supplemented by a Case Study of Implementing the Zebra Server
Under the Linux Operating System.
- NISO. 2007.
Z39.50 Resource Page -
National Information Standards Organization (NISO).
(Links to general information,
Z39.50 search services,
software, and news.)
- Techstreet. 2007.
Techstreet.com : ANSI/NISO Z39.50-2003 : Information Retrieval :
Application Service Definition & Protocol Specification, Z39.50-1995.
(The ANSI/NISO standard,
available for free download in PDF format.)
- U.S. Library of Congress. 2007.
Library of Congress WWW/Z39.50 Gateway.
(Web interface to many Z39.50 OPACs,
indicating vendors of server software
in many cases.)
Last updated April 16, 2007.
This page maintained by
Prof. Tim Craven
E-mail (text/plain only): firstname.lastname@example.org
Faculty of Information and
University of Western
Canada, N6A 5B7