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The Z39.50 Protocol in Plain English
Clifford A. Lynch
Division of Library Automation
University of California Office of the President
300 Lakeside Drive, 8th floor
Oakland, California 94610-3550
510/987-0522
[email protected] or
[email protected]
1. What is Z39.50?
Z39.50 is an American National Standard that was approved in 1988
by the National Information Standards Organization (NISO), an
American National Standards Institute- (ANSI) accredited
standards writing body that serves the library, information, and
publishing communities. Balloting has just concluded on a
revised version that will hopefully be adopted in 1992.
Z39.50 is an applications-layer protocol within the OSI reference
model developed by the International Standards Organization
(ISO). Its purpose is to allow one computer operating in a client
mode to perform information retrieval queries against another
computer acting as an information server.
The standard provides a uniform procedure for client computers to
query information resources such as server computers supporting
online library catalogs. For example, the development of a client
program running on one machine may provide end users with a
common means of access to a variety of information resources
attached to a computer network.
2. Does Z39.50 apply only to bibliographic data, or can other
types of information be accommodated?
While many of the initial applications of Z39.50 are for use with
bibliographic data (online public access library catalogs, for
example), the protocol is actually quite general, and search
attribute sets can be defined which allow the protocol to work
with most other types of data. Some specialized data, such as
images, may necessitate protocol extensions. Various groups are
currently exploring the area of protocol extensions, and are
defining attribute sets for other types of data, such as full
text.
3. Is Z39.50 an International Standard?
No. Z39.50 is an American National Standard. However, there is an
ISO standard called Search and Retrieval, ISO 10162/10163
(service and protocol documents, respectively), which was
formally adopted to International Standard (IS) status in 1991.
SR is almost identical to a subset of Z39.50. Z39.50 is being
revised to harmonize with SR, at which point the American
National Standard will be a compatible superset of the
International standard. These changes are included in the 1992
revision that has just completed balloting.
4. I have a GEAC (or any other) circulation system and a Carlyle
(or any other) online public access catalog at my library. Will
Z39.50 enable them to talk with each other?
In theory, Z39.50 provides a basis for allowing such
communication. However, attribute sets and data transfer formats
appropriate to queries of circulation systems by public access
catalogs have not yet been standardized, much less tested in
practice.
The National Information Standards Organization's Technical
Plan, which defines NISO's standards development agenda, calls
for work in this area.
In addition, for such a link to work, both vendors not only would
have to implement Z39.50, but they would have to integrate the
protocol implementation with their overall software applications
to create an effective intersystem link.
In a joint project involving Data Research Associates (DRA),
Digital Equipment Corporation (DEC), and the University of
California, a link will be developed between the DRA system being
installed at UC Davis and the UC campuswide MELVYL^melibm system,
which would allow the MELVYL system to perform Z39.50-based
searching of the circulation status file on the DRA system. This
searching would allow display of information on the availability
of materials as part of a MELVYL catalog display for material
held at the Davis campus.
5. Can I buy a Z39.50 package?
Today, I know of no organization that is marketing a Z39.50
client or server, although a number of the organizations that are
doing work in this area may be willing to share code. In the
longer term, Z39.50 "products" will probably fall into two
categories. There will be client implementations that run on
workstations or mainframes, and it is likely that at some point
we may see commercial products of this type that provide a user
interface to many Z39.50 servers. It seems much less likely that
we will see large numbers of Z39.50 server products that stand
alone since a Z39.50 server becomes an integral part of an
information retrieval application. We may see vendors of
information retrieval systems or database management software
offering Z39.50 toolkits or support as part of their overall
offerings. And it is likely that we will see vendors of
library-specific applications, such as the online library
catalogs offered by DRA and NOTIS, integrating Z39.50 server
and/or client support in their products.
6. What vendors are currently working on Z39.50? What other
efforts are underway?
There are a number of efforts underway; more are starting up all
the time. Here are some of the more elaborate projects (in no
particular order) that we know about as of early 1992:
- -- OCLC is working on Z39.50 server and client support for a
range of systems, including EPIC. OCLC has also done work with
NYSERNet in Z39.50. Contact: Ralph LeVan (OCLC, 6565 Frantz Rd.,
Dublin, OH 43017; (614) 761-6115;
[email protected]).
- -- RLIN is working on Z39.50 server and client support, and
Z39.50 is very much part of their strategic technical plan.
Contact: Madeline (Lennie) Stovel (RLG, Inc., 1200 Villa St.,
Mountain View, CA 94041-1100; (415) 691-2259; bl.mds@
@rlg.stanford.edu).
- -- Data Research Associates (DRA), a library automation vendor,
is developing Z39.50 support (client and server) for their
product. They are participating in a joint project with Digital
Equipment Corporation, and the University of California Office of
the President to build a link between a DRA system at UC Davis
campus and the MELVYL online catalog. This link would allow UC's
MELVYL system to perform Z39.50-based searching of the
circulation status file on the DRA system. Contacts: Clifford
Lynch (University of California Office of the President, 300
Lakeside Dr., 8th floor, Oakland, CA 94610-3550; (510)987-0522;
[email protected]). Mary Heath (University of
California at Davis, Shields Library, Davis, CA 95616;
(916) 752-0129;
[email protected]). Jim Michael (DRA, 1276 N.
Warson Rd., St. Louis, MO 63132-1806; (800)325-0888; jim@
@dranet.dra.com).
- -- The University of California Division of Library Automation
is developing client and server Z39.50 support with help from
Digital Equipment Corporation in conjunction with Pennsylvania
State University. This is both for the UC IBM 3090-based MELVYL
online catalog and the VAX 9000-based Pennsylvania State
University LIAS, as well as for selected microcomputers.
Contacts: Clifford Lynch (see above). Eric Ferrin (Pennsylvania
State University, E8 Pattee Library, University Park, PA 16802;
(814) 865-1818;
[email protected]).
- -- Project Mercury is a joint Carnegie-Mellon
University/OCLC/Digital Equipment Corporation project to develop
an electronic library at CMU. It is using Z39.50 as a central
element in linking clients and servers. Contact: Bill Arms
(Carnegie-Mellon University, 5000 Forbes Ave., Pittsburgh, PA
15213; (412) 268-2122;
[email protected]).
- -- UC Berkeley is developing an Information Server Project to
coordinate campus community information. The Berkeley Information
Server will use Z39.50 in a client-server architecture, with UNIX
servers and initial clients targeted for workstations and
personal computers. Contact: Margaret Baker (University of
California, 289 Evans Hall, Berkeley, CA 94720; (510)642-5601;
[email protected]).
- -- The Linked Systems Project is organized by the Library of
Congress, OCLC, and RLIN, which are currently interchanging
bibliographic and authority records using a predecessor protocol
to Z39.50 over an OSI network, with plans to upgrade to current
Z39.50 standards. Contact: Sally McCallum (Library of Congress,
Washington, DC 20540, (202) 707-5807; bb.shm@
@rlg.bitnet).
- -- The Florida Center for Library Automation is working on the
development of Z39.50 server and client functions for the NOTIS
library automation system. They have received a US Department of
Education Title II-D grant for the project. Contact: Mark
Hinnebusch (Florida Center for Library Automation, Suite 320,
2002 NW 13th St., Gainesville, FL 32609; (904) 392-9020;
[email protected]).
- -- Thinking Machines Corporation (TMC) has distributed code for
the Wide Area Information Server (WAIS), a Z39.50-based set of
client and server software. Servers run under UNIX and Connection
Machines; clients are available for a wider range of machines.
WAIS is based on earlier work by TMC, Dow Jones, and Apple
Computer on the development of a prototype information server for
a Dow Jones database based on a somewhat extended and modified
Z39.50 protocol. Contact: Brewster Kahle (Thinking Machines, 245
First St., Cambridge, MA 02142; (617) 234-2874; brewster@
@think.com).
- -- There is an active implementors' group for Z39.50 which meets
every few months, chaired by Mark Hinnebusch (Florida Center for
Library Automation, Suite 320, 2002 NW 13th Street, Gainesville,
FL 32609; (904) 392-9020;
[email protected]). They run
a network mailing list called Z3950IW at nervm.nerdc.ufl.edu and
nervm.bitnet. Contact: Mark Hinnebusch for subscription
information. An FTP file server containing Z39.50 documents is
also available.
- -- A Z39.50 testbed has been established under the auspices of
the Coalition for Networked Information (CNI). This group, which
includes about 15 organizations, plans to develop and demonstrate
multiple interoperable Z39.50 implementations running over the
Internet within a short time frame. Contact: Clifford A. Lynch
(see above).
7. When can I see a Z39.50 implementation?
There are several running prototypes today, such as CMU Project
Mercury, which was shown at EDUCOM '89 in Ann Arbor. It seems
likely that you will see demonstrations at meetings of groups
such as NET '92 and EDUCOM during 1992.
8. How do I get a vendor to write a Z39.50 interface?
Today, most library automation local system vendors do not seem
to have firm plans to implement Z39.50. You need to make it
clear to vendors and potential vendors that this is an important
feature for the future, and to consider needs for Z39.50 in
procuring new systems.
9. How do I get a copy of the Z39.50 standard?
Order from Transaction Publishers, Rutgers -- The State
University, New Brunswick, NJ 08903; (201) 932-2280. Transaction
publishes NISO standards. You can contact NISO at National
Bureau of Standards, Administration 101, Library E-106,
Gaithersburg, MD 20899;
[email protected].
You may also want to track ISO 10162/10163 (available from
Omnicom Information Service, 115 Park Street, SE, Vienna,
Virginia 22180; (703) 281-1135; or from NISO), and subscribe to
the Z39.50 implementors' mailing list (see above). The Library
of Congress is serving as the maintenance agency for Z39.50 on
behalf of NISO. Contact: Sally McCallum, Network Development
Office/Processing Services, Library of Congress,
Washington, DC 20540; (202) 707-6237.
The following books and papers may also be of interest for more
information. The paper by Lynch and Preston contains a much more
extensive bibliography.
Henriette D. Avram. "The Linked Systems Project: Its
Implications for Resource Sharing," Library Resources
and Technical Services (January/March 1986), 30:1; pp. 34--46.
Henriette D. Avram. "Toward a Nationwide Library Network,"
Journal of Library Administration (Fall/Winter
1987), 8:3/4; pp. 96--115.
Henriette D. Avram. "LSP and Library Network Services in the
Future," EDUCOM Bulletin (Summer/Fall 1988),
23:2/3; pp. 52--58.
Henriette D. Avram. "Building a Unified Information Network,"
EDUCOM Bulletin (Winter 1988), 23:4; pp. 11--14.
Michael Buckland and Clifford Lynch. "National and International
Implications of the Linked Systems Protocol for Online
Bibliographical Systems," Cataloging and
Classification Quarterly (Spring 1988), 8:3/4; pp. 15--33.
Wayne E. Davison. "The WLN/RLG/LC Linked Systems Project,"
Information Technology and Libraries (March 1983),
2:1; pp. 34--46.
Ray Denenberg. "Linked Systems Project, Part 2: Standard Network
Connection," Library Hi Tech (1985), 3:1, Issue 10;
pp. 71--79.
Ray Denenberg; Bob Rader; Thomas P. Brown; Wayne Davison; and
Fred Lauber. "Implementation of the Linked Systems Project: A
Technical Report. Part One: Library of Congress. Part Two: The
Western Library Network. Part Three: The Research Libraries
Group. Part Four: OCLC," Library Hi Tech (1985),
3:3, Issue 11; pp. 87--107.
Judith Fenly and Beacher Wiggens (eds.). The Linked
Systems Project: A Networking Tool for Libraries (Dublin, OH:
OCLC, Inc., 1988).
Clifford A. Lynch. "Library Automation and the National Research
Network," EDUCOM Review (Fall 1989), 24:3; pp.
21--26.
Clifford A. Lynch. "Access Technology for Network Information
Resources," CAUSE/EFFECT (Summer 1990); pp.
15--20.
Clifford A. Lynch. "Information Retrieval as a Network
Application," Library Hi Tech (1990), 8:4, Issue
32, pp. 59-74.
Clifford A. Lynch. "The Z39.50 Information Retrieval Protocol:
An Overview and a Status Report," Computer Communication
Review (January 1991), 21:1; pp. 58--70.
Clifford A. Lynch. "The Client-Server Model in Information
Retrieval," Interfaces for Information Retrieval
(Martin Dillon, ed.) (Westport, CT: Greenwood Press, 1991); pp.
301--318.
Clifford A. Lynch and Cecilia M. Preston. "Internet Access to
Information Resources," Annual Review of Information
Science and Technology (ARIST) Volume 25 (New York, NY:
Elsevier, 1990); pp. 263--312.
Sally H. McCallum. "Linked Systems Project, Part 1: Authorities
Implementation," Library Hi Tech (1985), 3:1, Issue
10; pp. 61--68.
Michael J. McGill. "Z39.50 Benefits for Designers and Users,"
EDUCOM Review (Fall 1989), 24:3; pp. 27--30.
Michael J. McGill; Larry L. Learn; and K.G. Thomas. "A Technical
Evaluation of the Linked Systems Project Protocols in the Name
Authority Distribution Application," Information
Technology and Libraries (December 1987), 6:4; pp. 253--265.
10. Why should I care about Z39.50? Why is it important to
my library? If it's so important why haven't I heard more about
it?
Z39.50 is important because it is the best technology we have
today to permit a single user interface to access the
multiplicity of information resources becoming available on the
national network.
The need for Z39.50 is just now becoming clear to a larger
community as network information is becoming a more serious
issue. You might want to become involved in the overall movement
towards network information resources. Write the ARL/EDUCOM/CAUSE
Coalition for Networked Information (Paul Peters, Director, 1527
New Hampshire Ave., NW, Washington, DC 20035; (202) 232-2466;
[email protected]).
