Schemes to add functionality to the web OPAC fall into four categories: web OPAC enhancements, web OPAC wrappers, web OPAC replacements, and integrated library system replacements. I'm outlining these four techniques in a report I'm editing for an OhioLINK strategic task force and a bit of a reality check on this categorization is desired, so if I'm missing anything big (conceptually or announcements of projects/products that fall into these categories), please let me know in the comments. Generally speaking, this list is ordered by cost/complexity to implement -- from lowest to highest -- as well as the ability to offer the described enhanced services from least likely to most likely.
Web OPAC enhancements are functions that are added to the existing web OPAC system. This most often entails additional product purchases from the automation vendor, such as the optional enhancements in WebPAC Pro for Millennium OPACs or content solutions in SirsiDynix. Enhancement can also be added through creative use of an existing web OPAC's template functions, such as the method by which LibraryThing for Libraries can be added to OPAC displays.
Web OPAC wrappers use the existing web OPAC provided by the integrated library system as a source of information, but hide that information behind a completely new interface. The intervening system get that information from the integrated library system through a variety of mechanism. In some cases, it may be possible to use established protocols (such as Z39.50) or programming interfaces (such as an XML content server). In cases where such functionality is not available from the underlying integrated library system, a "screen-scraping HTML" technique may be required. ((Such a technique gets the information from the ILS using the existing web OPAC. Such schemes are generally fragile because changes to the underlying web OPAC can have detrimental affects on the content scraping process.))
One example of such a wrapper is the work at Ann Arbor Public Library on SOPAC. Short for "Social OPAC," SOPAC is "a set of social networking tools integrated into the AADL catalog [that] gives users the ability to rate, review, comment-on, and tag items." ((Blyberg, J. (2007). AADL.org Goes Social. blyberg.net. Retrieved October 12, 2007, from http://www.blyberg.net/2007/01/21/aadlorg-goes-social/)) It uses an open source content management system called Drupal as a structure through which the added functionality is provided. For example, when a user seeks the bibliographic information page for a catalog record, that request is made from the user's browser to the Drupal software. The Drupal software in turn makes a request to the integrated library system for the bibliographic information it holds. The response from the ILS is parsed by the Drupal software for key information such as title, author, subjects, holdings, etc. This information is mixed with information stored in the Drupal database (ratings, tags, reviews, cover images, etc.) and a new web page is created and returned to the user's browser.
Another example of a web OPAC wrapper is Scriblio (formerly called WPopac). Using the underlying framework of Wordpress, Scriblio offers faceted browsing, tagging, and syndication feeds for the underlying Millennium WebOPAC. Scriblio is a project of Plymouth State University, supported in part by the Andrew W. Mellon Foundation. Both SOPAC and Scriblio are available under open source licenses.
Web OPAC replacements are new systems that completely replace the existing web OPAC. Unlike wrappers (which get their bibliographic data in real-time from the underlying web OPAC), these replacements operate on sets of records that are extracted from the ILS or come from another source. (In some cases, these replacements still rely on the underlying web OPAC as a source of item status information such as checked out status and due date.) The first notable OPAC replacement was at North Carolina State University when its library installed and configured the Endeca software to provide a faceted browse to the library catalog. By itself, an Endeca OPAC display does not enable tagging, annotation, or user aggregation services such as recommendation engines. Other similar web OPAC replacements are Encore from Innovative Interfaces ((As Betsy Graham, Vice President of Product Management at Innovative Interfaces, notes in the comments, the Encore will perform real-time queries to a Millennium ILS for bibliographic data, and in such cases the data extract is not needed.)), Primo from Ex Libris and Aquabrowser from Medialab Solutions. Miami University's experiments with the open source Apache SOLR and the exported records from their Millennium system also fall into this category. Worldcat Local is also a form of web OPAC replacement noting that the source of bibliographic records is the OCLC Worldcat database rather than the local ILS.
ILS replacements offer the biggest opportunity for enhanced user services, particularly by adopting one of the open source solutions now available. At this time, neither of the open source solutions (Evergreen and Koha) offers more than faceted search and browsing. Unlike the commercial systems, however, the source code of the system can be modified to add these functions, and the modifications shared with other users of the same system.
[Update 20071015T1624 : Corrections made -- and the text improved! -- based on Betsy Graham's comment. Thanks, Betsy!]
The text was modified to update a link from http://www.iii.com/mill/webopac.shtml to http://web.archive.org/web/20071015145500/http://iii.com/mill/webopac.shtml on January 20th, 2011.
The text was modified to update a link from http://www.iii.com/encore/main_index2.html to http://web.archive.org/web/20080328163000/http://www.iii.com/encore/main_index2.html on January 20th, 2011.
The text was modified to update a link from http://www.sirsidynix.com/Solutions/Products/portalsearch.php#content to http://web.archive.org/web/20071109170053/http://www.sirsidynix.com/Solutions/Products/portalsearch.php#content on January 28th, 2011.