The development of online bibliographic databases and the rapid growth of online services accessible on the internet and world wide web (WWW) has made it possible to access information in ways not possible before. Libraries, whose primary mandate is to provide information, shifted the emphasis from collecting the information in hard copy to accessing information through electronic resources.

1. Dr.P.PADMA
Assistant Professor
DOLIS
Z39.50 :An Information Retrieval
Protocol

2. Introduction
 The development of online bibliographic databases and the rapid
growth of online services accessible on the internet and world
wide web (WWW) has made it possible to access information in
ways not possible before. Libraries, whose primary mandate is to
provide information, shifted the emphasis from collecting the
information in hard copy to accessing information through
electronic resources.

3. Contd..
 However, the major problem is of variation in software and
hardware. Library professionals have to learn the specific features
of each system, i.e., command languages, search procedures, etc.
More the electronic resources grow; more will be the confusion
on how to access the information of so many diverse databases.
Another problem is the ability of many diverse database
structures and different application designs to exchange
information electronically.
 ANSI/NISO, Z39.50 standard was developed to share the
bibliographical information electronically and to overcome the
problems of database searching with many search languages.

4.  A standard presents an agreement on how to
do something or carry out some activity to
arrive at predictable results. All standards
published by the National Information
Standards Organization (NISO) are developed
by a consensus process that draws on the
expertise of implementors and vendors,
product developers , and users of those
products they are approved by the American
National Standards Institute.
What is a
Standard?

5. Why standards
are necessary
?
 Standards are necessary for
networking and for information
exchange. Eg. MARC and
Z39.50 allow searching, retrieval
and exchange of records across
platforms and its Unicode allows
encoding, searching and retrieval
of information in different
scripts.

6. Library Automation Standards:
 Standards adopted by the library industry and community which
facilitate data interchange between libraries and institutions and
are supported by most systems are MARC (Machine Readable
Cataloguing) standards and Z39.50, the information search and
retrieving protocol standard

7. WHAT IS Z39.50 Protocol?
 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. It
is covered by ANSI/NISO standard Z39.50, and ISO standard
Z39.50. The standard's maintenance agency is the Library of
Congress.
 Z39.50 is widely used in library environments, often incorporated
into integrated library system and personal bibliographic
reference software. Interlibrary catalogue searches for interlibrary
loan are often implemented with Z39.50 queries.

8. Contd..
 Z39.50 is an international standard protocol used by net- worked computer systems
for information retrieval.
 It enables information seekers to search different systems on a network or the
Internet through the use of a single user interface.
 Software and system vendors offer access to information from a diversity of unique
systems with different hardware, software, interfaces, and data-base search
commands.
 The goal of Z39.50 is to reduce the complexity and difficulties of searching and
retrieving information.
 Z39.50 makes it easier to use the wealth of information re- sources on the Internet.
 When using Z39.50-enabled systems, a user in one system can search for electronic
information in another system without having to know how that system works .

9. History
 The name Z39.50 comes from the fact that the National Information
Standards Organisation (NISO), a standard developer for American
National Standards Institute(ANSI) was once the Z39 committee of
ANSI.
 NISO standards are numbered sequentially and Z39.50 is the fifth
standard developed by NISO.
 NISO approved the original Z39.50 standard in 1988 . It was developed
as an application layer of the OSI(Open System Interconnection)
communication model.
 Z39.50-1988 is now out-dated and incompatible with later Z39.50
versions. It formed the basis of the wide area information server
(WAIS) protocol.

10. Contd..
 Z39.50 has progressed through three versions, with each version adding vastly greater
functionality and sophistication.
 Version 1 defined the core services of Z39.50.
 Version 2 formalized the structure of information to be exchanged based on the ISO
standard data description language and encoding rules known as ASN.1 and BER. With
consensus on Z39.50 version 2, vendors began to create applications rapidly and
momentum grew for compliance with Z39.50 functionality.
 Version 3, the current version of the standard, builds on and includes version 2. Version
3 is extremely powerful in its support for simple to highly complex applications.
 The current version of the Z39.50 standard is formally known as ANSI/ NISO Z39.50-
1995, Information Retrieval—Application service definition and protocol specification.
 The International Organization for Standardization (ISO) approved two information
retrieval standards in 1993 (ISO 10162 and ISO 10163-1). In 1998, ISO adopted the
Z39.50 protocols and issued ISO 23950.

11. How does Z39.50 work?
Z39.50 operates in a client/ server
environment, acting as a common
language that all Z39.50-ewnabled
systems can understand.
Most Z39.50 implementations use the standard
TCP/IP Internet communications protocol to
connect the systems and Z39.50-compliant
software to translate between them for search and
retrieval.
For Z39.50 communication and
interoperation to take place, both the
client and the server must be able to
speak the Z39.50 language.
To the users this all happens behind the scenes;
they simply see their familiar search and display
inter face.

12. Contd..
To achieve this interoperability,
Z39.50 standardizes the messages
that clients and servers use for
communication, regard- less of
what underlying soft- ware,
systems, or platform are used.
Z39.50 supports open
systems, which means it
is non- proprietary, or
vendor independent.
Z39.50 governs how the
client translates the search
into a standard format for
sending to the server
After receiving the search, the server uses
Z39.50 rules to translate the search into a
format recognized by the local database,
performs the search, and returns the results
to the user’s client.
The client’s user interface software
processes the results returned via
Z39.50 with the goal of displaying
them as closely as possible to the
way records are displayed in the
user’s local system.

13. Solutions of
Z39.50
 Originally Z39.50 was designed to help with searching
very large bibliographic data- bases like those of OCLC
and the Library of Congress.
 Z39.50 is used for a wide range of library functions that
involve database searching, from cataloguing to
interlibrary loan to reference.
 With the rapid growth of the Internet, the Z39.50
standard has become widely accepted as a solution to
the challenge of retrieving multimedia information
including text, images, and digitized documents.
 Z39.50 is being used to access, for example, museum
data, government information, and geospatial data.
 It can also be used to search the online databases and
CD-ROMs that vendors develop according to a variety
of design schemes. With- out having to learn each
system, users can search those databases with a single
Z39.50 client, even though each uses a different
hardware and software configuration, stores different
types of data, and has different internal search logic.

14. Benefits
 Seamless access: This seamless access to multiple,
diverse databases through a single interface is Z39.50’s
greatest benefit.
 Resource sharing:Z39.50 can encourage
 rebroadcast searching of library catalogues located on
the Internet anywhere in the world,
 interlibrary loan through Z39.50’s standardized
approach for delivering holdings information, and
 online item ordering and document delivery.
 Increased Productivity
 Staff training time can be reduced for functions that
require database searching, such as cataloguing,
acquisitions, and interlibrary loan.
 Easier access to electronic resources reduces all users’
time spent in searching for relevant information.

15.  The basic function of Z39.50 is to negotiate a connection be-
tween the client and server on two systems, execute a search, and
return the formatted results to the user’s screen.
 In a Z39.50 session, the Z39.50 client soft- ware that initiates a
request for the user is known as the Origin.
 The Z39.50 server software system that responds to the Origin’s
request is called the Target
Key features of Z39.50

16. Facilities and services
 Z39.50 is divided into eleven basic facilities. Each facilities. Each facility is
divided into one or more service. A service facilitates a particular type of
operation between the client and the server out of eleven facilities, three are
core facilities and they are
 Initialisation,
 Search and
 Retrieval.

17. Initialisation
 The Initialization Facility allows the Origin
(client) and Target (server) to negotiate and
establish a Z39.50 search session, known as a
Z-Association. This facility establishes the rules
by which the client and server will operate.
Establishing the rules involves sharing
information about the version of the protocol
being used by client and server, default
character set, size and limits on records to be
transferred, and other Z39.50 features, e.g.,
sorting, browsing, and deleting result sets.

18. Search Facility
 Allows the user to formulate a search query
using an interface format familiar to the user.
Z39.50 provides a rich vocabulary for ex-
pressing search queries. The user may identify
specific fields to search (i.e., access points)
and may create complex searches using
Boolean operators, truncation, and other
advanced searching techniques. Z39.50 also
supports the main- taining of multiple search
results and combining the results of those
searches.

19. Present Facility
 Allows the user to request that some or
all of the records identified as meeting
the search criteria be transmitted from
the server to the client. This facility also
sup- ports selection of data elements to
include and format for transferring the
records.

20. Other Z39.50 Facility protocols exist to
support such features as
 Sort the results as specified by the user.
 Delete search results, either entirely or for specified re- cords.
 Scan (browse) through index lists of items such as subject terms,
titles, author names, and other database fields.
 Access Control through authentication and passwords.
 Resource Control and termination of Z39.50 search sessions by
the client or server.

21. Contd..
Two newer facilities, not readily available yet in
many implementations are
Explain
 Which allows the client to exchange information
with the server about what type of server the client
is querying and what the client must do to
communicate successfully with that server in a
Z39.50 session, and
Extended Services
 Which define operations the client may request of
the server, such as saving a search for later re-use
or running a search query on a periodic schedule.

22. Advantages of Z39.50
 Any database that is Z39.50 enabled may be searched by using a single
search interface a single set of search commands and search strategies.
 Allows intersystem searching and record transfer irrespective of different
software and hardware.
 Multi-database searching using single search interface.
 Virtual union catalogue--a combined catalogue of several libraries on
diverse systems (without merging the catalogues) is possible. Z39.50
clients will permit searching of members' collections with a single
interface.
 Interlibrary loans (ILL) process will be made easier. Extended services for
ordering documents, updating databases and sorting searches can be
defined and controlled via Z39.50.
 Records can be displayed in any flavour of MARC. In addition, work is
going on to use generic set of data element called Dublin , Core to use as
attribute set and record syntax.
 CD-ROM databases from various vendors could be searched with a single
interface. The time and expense of training users on multiple interfaces
could be reduced.
 The SDI or selective dissemination of information service could be set to
run a saved search in the catalogues of many different libraries regularly
and automatically with results being sent to the user by fax or e-mail

23. DISADVANTAGES OF Z39.50
Very complex.
Levels of services supported within and between the particular implementation depend on Z-client-server
and host library management system.
The differences between the facilities on 2-client and 2-server lead to poor output.
Multi-database searching leads to slow response time and information overload.
Any database that is Z39.50-enabled may be searched by using a single search
Multi-database search interface.

24. Conclusion
 The Z39.50 protocol not only rescues a librarian
from learning different search interfaces for
different databases, it also helps the librarian to
improve resource sharing among libraries by
virtual union catalogue and ILL. Z39.50 also
allows users to specify search statement to be
saved and run at intervals. This greatly helps the
librarian in providing the SDI service.