Librarians investigating the selection of automated library systems are increasingly encountering references to PAC's (public access catalogs). PAC's- online catalogs which can be accessed by library users without assistance from staff are still very much in the developmental stage. Even so, some fifty libraries now have some form of patron access catalog, approximately half of which are mounted on minicomputer based turnkey systems.
Although there is not yet an established body of opinion as to what constitutes a patron access catalog (PAC) the following elements-in addition to those which normally apply in the selection of an automated system-deserve consideration:
- Data base design and content
The data base which supports a patron access catalog need not necessarily mirror the contents and practices of card catalogs which frequently contain only a limited selection of the items held in a library. In a PAC data base not all formats might be represented by equally long records. A library should decide what it wishes to include and ensure that the appropriate formats can be accommodated.
The system should be able to accept, store and reproduce full-MARC bibliographic records. Since the cost of maintaining full records on-line will be significant and some libraries may not feel that they need them, the system should also be able to accommodate partial records that are MARC compatible.
To facilitate the input of original records, the system should provide an appropriate MARC work form display and a substantial amount of input support and error checking.The system should permit a library to select the specific fields it wishes to include in its data base and to include an adequate amount of information in each.
- Authority control
Subject, name and series authority files must be available online and must be capable of being maintained on a current basis. The system should support a fully automated, interactive authority control system in which each heading in the authority files is linked to each occurrence of that heading in the bibliographic file, permitting automatic updating of all occurrences of a heading through a single machine transaction.
- Number of access keys
The number of access keys-the points through which information can be retrieved-should, at least, be as numerous as the access points available to users of a card or CON (computer-output- microform) catalog. Theoretically the number of keys may be unlimited, but practically there is a point beyond which the cost in terms of system performance and the amount storage for indices becomes unacceptable. A library should determine the limit for its particular system and compare that with a list of the access keys it desires.
It should not be necessary to use derived or algorithmic keys made up of combinations of letters from author's names and the title or other elements of the entry. Such an approach is unacceptable in an on-line catalog designed for patrons with little experience in using computer terminals.
- Subject access
A patron access catalog should offer substantially better subject access than the 1.5 average Library of Congress subject headings typically associated with each record in a traditional catalog. Free-text searching of title and subject fields should also be available. The system should permit Boolean searches using AND, OR, and NOT relationships as this technique offers a dramatic improvement in access over card or COM catalogs.
- User cordiality
One of the major reasons for providing patron access catalogs is to promote the identification and location of information by patrons without the assistance of library staff. To do this successfully the system must be easy to use. This can be achieved by careful selection and development of the hardware and software. Terminal keys can be color coded or touch terminals can be used so that the user does not have to search a keyboard for the right keys. Software can be written to provide prompts to guide the user.
There are disadvantages to these easy-to-use terminals: the experienced user may become impatient with the deliberate and gradual nature of the prompts. An ideal system would employ terminals with keyboards and would offer bath prompt and command modes to that experienced users could skip the prompts and fully control the system.
- Display and print formats
A PAC needs a variety of display and print formats. Displays should include a format that resembles the catalog card and other formats which emphasize the portions of a record that are of primary concern to the library's clientele. The system should provide an appropriate method of displaying multiple records when a search results in more than one hit. An abbreviated format will allow the simultaneous display of several records, but it should be extensive enough to facilitate meaningful comparisons. The entire record should be available upon a simple command. The appropriate display for a "full" record for a patron will be different from that for a cataloger. The system should allow the user to browse or page forward or backward to examine related entries.
The terminals should be able to support printers. Printers normally reproduce that which is displayed on the screen. The use of a printer with a terminal that displays only full bibliographic records would tie up terminals and might force patrons to wait too long. If the software does not permit the printout to be limited to a single line of information per record, printing should be done off-line and only when specifically requested by the patron.
- Number of terminals
At this stage there is little evidence on which to estimate the number of on-line terminals a library should install for its public access catalog. PACs which offer sophisticated searching capabilities such as Boolean logic will probably require more terminals than the number of COM readers needed to support a microform catalog. One CON reader for each 200 patrons using the library in a day is an accepted rule of thumb for most libraries: an on-line catalog might require one for each 100 daily users. A library might size the system on the 1:100 formula and budget on that basis, but install on the basis of 1:200 and use the system's auditing and reporting features to adjust the number to the correct level.
This list of elements, supplemented by those which apply to all automated systems-back-up, transferability of software, capacity for expansion, five year cost, etc. should be taken into account when planning or evaluating patron access catalogs. The list will change over the next year as more libraries gain more experience with PACs. The professional literature should be followed carefully and those planning to implement patron access catalogs should seek to correspond with librarians at the institutions which have already launched their efforts.
