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Unit 7: Online Public Access Catalogue (OPAC)

The interfaces, which were usually menu-driven, replicated traditional catalogues in their form Notes
of access by providing mainly phrase access to separate subject headings, title, and author
indexes (Mitev, 1989: 144).

Notes Output and display of search results generally had a single format.

Second-generation Online Catalogues

With further developments in information technology, it was possible to provide a more
sophisticated system for input, storage and output of bibliographic information. Second-
generation online catalogues are a departure from traditional card catalogues and incorporate
many new features for the provision of effective access. In contrast to the limited input, storage
and output capabilities of first-generation online catalogues, second-generation online catalogues
are characterised as being powerful tools for the searching of bibliographic information.
Keyword search, Boolean keyword search, cross index search and increasing or reducing of
search results are among the features of second-generation online catalogues (Matthews, 1991:
11). Hildreth (1987: 650-651) writes:
Today’s second-generation online catalogues represent a marriage of the library catalogue and
conventional online information retrieval (IR) systems familiar to librarians who search online
abstracting and indexing databases via DIALOG, BRS, ORBIT, MEDLINE, etc. Improved card
catalogue-like searching and browsing (via headings and cross references) capabilities have
been joined with the conventional IR keyword and Boolean searching approaches. Many online
catalogues support the ability to restrict searches to specified record fields, to perform character
masking and/or right-hand truncation, and to limit the results by date, language, place of
publication, etc. Also, bibliographic records may be viewed and printed in a number of different
display formats.
However, it should be noted that there are a number of major differences between online
catalogues and these IR systems that make second-generation online catalogues easier searching
tools (Ibid: 651). With a combination of different search methods, the user is offered possibilities
that were not available in first generation online catalogues.
Due to improvements in the design of database management software, the structure and content
of bibliographic records in second-generation online catalogues may be enhanced by
incorporating full records augmented by information such as tables of contents, summaries,
content notes, abstracts and links to full electronic texts. Considerable increase in the length of
fields was another improvement in second-generation systems.
Interfaces are usually in two modes, menu-driven and command-driven; this makes the
interaction between the user and the catalogue more flexible. In terms of user assistance, these
catalogues provide more options including, for example, help screens, error messages and
suggestive prompts. Ease of use and user-friendliness are two major features of today’s second-
generation online catalogues.

Third-generation Online Catalogues

As mentioned earlier, only a few systems have moved beyond second-generation online
catalogues into third-generation online catalogues with enhanced or more sophisticated features.
Due to the growing sophistication and availability of technology, new capabilities are being
added to online catalogues making them more adaptive to the needs of library patrons. Free text
search, enriched database search and simultaneous journal citation searching are among the
retrieval capabilities in third generation online catalogues.

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