Supercomputer

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Information sources and services

Stuart Ferguson, Rodney Hebels, in Computers for Librarians (Third Edition), 2003

Other portable databases

CD-ROM is the principal offline computer-based alternative to online search services. It is worth remembering, however, that CD-ROM is not the only offline product available.
Some online database producers, for example, have on occasion provided subsets of their databases on magnetic diskette for microcomputer use. It is feasible for customers of such a service to supply a profile of interests and, on the same principle as SDI, receive a custom-designed subset of the database for local use. One reason for the use of floppy disk for such services, and not CD-ROM, is that at present it is more appropriate for the delivery of information that requires frequent updating. All that is required is one person with a microcomputer and diskettes to create and update a database (and a postal service for delivery).
In the reference environment, CD-ROM is the main optical disk resource. The only other optical disk mentioned in surveys of optical disks in libraries – as far as information resources are concerned – is the videodisk, which is larger than a CD-ROM and enjoyed a small market niche as an interactive multimedia product, for example, in computer-assisted learning packages, as well as an entertainment market.

Hypertext search facilities

Typical CD-ROM search facilities are much the same as those described for online searching, being based on the same text retrieval principles and employing similar search operators (for example, boolean operators) and search strategies. Accordingly, they share some of the advantages and disadvantages of online search facilities. The success of the search relies principally on the searcher's skilled use of search operators, field specification and choice of terms.
Given the problems of text retrieval in a large information source, however, it is worth considering hypertext as an alternative solution to text management problems. As discussed in Chapter 1, hypertext is an important component of Web publishing, as part of the markup language used to format Web documents (HTML) and as part of the retrieval method (HTTP). It provides users with the opportunity to follow associative links from document to document, or in other words surf the Net. Hypertext also has applications in the reference environment, since hypertext and hypermedia have been used in a number of CD-ROM products. Consider, for example, electronic encyclopedias, which consist of discrete nodes of text, linked not just to other nodes of text, but also to graphics, sound and video excerpts.
Obviously, not all forms of publication are well suited to the hypertext approach, but some reference sources are, for instance, encyclopedias, handbooks and guides.