Online Public Access Catalogue (OPAC) and its characteristics

The Information Explosion has revolutionized the thinking and outlook of the librarians during recent years. This phenomenon has triggered a series of changes posing corresponding challenges necessitating the re-examination of technical policies of library and information centers. Traditionally, one of the keys to retrieve the information has been the catalogue along with classification. OPAC

The catalogue which started in the hook form did not remain stable. It went on growing in its character and complexities over the years both in the physical and inner forms. The users of the library system expected certain advantages from the catalogues. But they have always remained incomplete and deficient. The catalogue throws into two forms – Physical and Inner forms. In reality, they are two sides of the same coin. As the users’ information-seeking behavior changed, corresponding changes have been expected from the catalogues. Nevertheless there have been failures of the physical forms, to fulfill the expectations of the catalogue users. The current users expect physical form catalogue to be an effective, easy to use, efficient, reliable, compact and helpful system to deliver information about the documents in the library and information center.online-public-access-catalogue

The long era of traditional cataloguing ended with the introduction of Information Technology (IT). The developments in IT has forced the librarians in the direction of adopting new physical forms of catalogue, one such being Online Public Access Catalogue (OPAL).

Online Public Access Catalogue (OPAC):

OPAC is an acronym for “On-line Public Access Catalogue”. It is an access tool and resource guide to the collection of a library or libraries which provides bibliographic data in machine-readable form and can be searched interactively on a computer terminal by users.


Pierre Le loarer’ defined OPAC as” a database describing documents via bibliographic entries composed of fields some of which may be queried (essentially the author, title and subject fields for querying by the public)

  • a query function providing access to the database indexes: the user specifies the field (ie criterion) via which he or she wishes to query the catalogue. Either that or the system implicitly chooses several criteria (access to a general index) and then suggests the entries found under the different’, criteria, according to the result of the search…
  • and (in some cases) a set of referential or authority lists that allow a given item(a document’s author, subject or language)to be consistently expressed in the same way, in the database and consequently retrieved in the same form.”

Gorman has characterized an on-line catalogue as an “integrationist” and defined it as “a bibliographic control system that allows access by means of a number of access points (conventional and “unconventional”; single and in combination).

Thus OPAC is a systematic record of the holdings of a collection. Its purpose is to enable a user of the collection to find out the physical location of the information in the collection. It is an access tool and resource guide to the collection of a library or libraries which provides bibliographic data in machine-readable form, facilitates search interactively on computer terminal by a user.

According to Hildreth, “Literature definitions of the online catalog fall into three categories, each representing a different perspective or model of the library catalog as the systematic record of a library holdings or as an access mechanism. The first category requires that the online catalog provide at least as much data content, organization, and access as the card catalog. The second category limits the online catalog to the data content, functionality, or usability of the card or book catalogs. The third category points beyond the traditional catalog forms and prescribes more data access, functionality, guidance, and usability than is possible with the pre-online, manual catalogs”.

Characteristics of OPAC:

An online catalogue generally includes the characteristics listed below:

  • A. It is a bibliographic control system that allows access by a number of access points to the bibliographic data stored in a machine-readable form;
  • B. Instructional help is provided;
  • C. It displays search results in a readily understandable form;
  • D. An interactive information retrieval system;
  • E. Boolean operators for search refinement are provided;
  • F. It is an interactive catalogue with the potential to overcome the major limitations of earlier forms of catalogues;
  • G. The use is no longer boring to the searcher, rather, it is more interesting;
  • H. The updating of the catalogue can be done in a short span of time;
  • I. The contents of OPAC are not restricted to the holdings of the particular library rather it can include the holdings of a number of libraries; and
  • j. OPAC may also provide information on the following:
      1. The holdings of contents of periodicals;
      2. A variety of databases,including full text files;
      3. Integration of acquisition and circulation;
      4. Instructions to use the OPAC; and
      5. Information about the library and community events.

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