Page 128 - DLIS007_LIBRARY AUTOMATION

Unit 7: Online Public Access Catalogue (OPAC)

Library, place reservations for items on loan, browse or cancel the reservations you have made, Notes
renew items you have borrowed, and view status/record of your library account, etc.

7.1 Meaning of Online Public Access Catalogue (OPAC)

An Online Public Access Catalogue (OPAC) is a computerized online catalogue of the materials
held in a library, or a library system. OPACs are often part of an integrated library management
system or software. The library staff and the public can usually access it in computers within the
library, or from home via the Internet. Since the mid-1980s, it has replaced the card catalogue in
most libraries. Since the mid-1990s, character-based OPAC interfaces are being replaced by
Web-based interfaces. Today more complex OPACs offer a variety of search capabilities on
several indexes, integrate rich content (book covers, video clips, etc.), and offer interactive
request and renewal functionality.
Most integrated library systems offer a browser-based OPAC module as a standard capability or
optional feature. OPAC modules rely on pull down menus, popup windows, dialog boxes,
mouse operations, and other graphical user interface components to simplify the entry of search
commands and formatting of retrieved information. Many libraries have their catalogues
accessible via Internet; some of them can be queried using a simple browser, other using a
special version of browser (with JavaScript and CSS features), and some others using Z39.50
clients. If one has few elements to identify a document, then he/she can use a meta-searcher
where he/she can fill the query form once and spread his/her query over many library catalogues.
The OPAC has many advantages over card catalogues. It can store entries; it can add new entries,
withdraw entries and print out updated version of a catalogue in book, card or shelf form. It can
also be used to search and produce catalogue in CD, DVD, etc. It itself can be used as a catalogue
cabinet with enhance features i.e. information can be stored within the computer and kind of
entries required can be easily got as and when required. It has also the facility to input the data
from the point of origin and output data can be transmitted directly to the place where it is
needed by using teleprocessing.
An OPAC database records are usually derived from the MARC format. The records are brief
bibliographic descriptions enriched with a small number of controlled subject descriptors (often
taken from the Library of Congress Subject Headings) and a classification number (usually a
Library of Congress or a Dewey decimal class number). The database records, thus, contain
minimal information for searching – little more than the author, title, publication year, subject
description, and a class number. The subject descriptors are selected to reflect the subject content
of the item as a whole rather than to provide in-depth indexing of the information contained in
the item.

Example: If a book contains many articles, subject descriptors are not assigned for each
article but only to the overall topic of the book.
For periodical publications, only the periodical as a whole is described. Individual journal
articles are usually not recorded in the database. This is in contrast to indexing and abstracting
databases that provide keyword searching in the abstract and even the full text of articles, and
provide exhaustive indexing of the content of journal articles. However, the distinction between
OPACs and other kinds of information retrieval systems is blurring. Increasingly, OPACs are
also providing links to full-text document, electronic books, and Internet resources.

Did u know? Most of the online catalogues in use today are what Hildreth termed
second-generation OPACs.

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