Released for public access over the Internet in early 1998, the Prints and Photographs Online Catalog (PPOC) (http://lcweb.loc.gov/rr/print/ catalog.html) is the most recent interface to an increasingly comprehensive catalog to the division's holdings.
The diagram is based on the experience of staff in the NDLP, in the custodial divisions whose content NDLP has helped digitize and provide access to, and in LC's central technology service organization, which has a small group of programmers building and maintaining the computer applications that support both American Memory and the Prints and Photographs Online Catalog. The framework in this diagram will be used to organize the observations and experiences described in this article.
Group-level catalog records for components of a large collection allow integrated general access from within LC's main catalog or the Prints and Photographs Online Catalog and identify the physical location and any paper-finding aid or index that offers more specific access.
To give users the clues offered by captions for neighboring images, a feature was added to American Memory and the Prints and Photographs Online Catalog that allowed visual browsing as a grid of thumbnail images sorted by call number.
One characteristic of the Prints and Photographs Online Catalog and American Memory that is not provided in most library catalog systems, which developed primarily as tools for organizing holdings of independent monographs, is the clear delineation of a collection.
The HABS/HAER records (for which the National Park Service maintains the data) are not converted to the MARC format but to a simpler format easily indexed by the search engine used for American Memory and the Prints and Photographs Online Catalog. This format identifies fields within records by labels in angled brackets (similar to SGML or HTML) and is easy to generate from any database software and to manipulate using simple programs or scripts.
In the Prints and Photographs Online Catalog, the uncontrolled terms are displayed separately, labeled as Topics rather than Subjects.
American Memory and the Prints and Photographs Online Catalog rely on InQuery (from Sovereign Hill Software, recently acquired by Dataware Technologies), a search engine, developed for indexing free text, that can recognize fields in tagged records or documents.
For the Prints and Photographs Online Catalog, the ability for users to search by creator, title, subject, and various numeric identifiers, such as call number, was considered essential.
Compared with earlier catalog systems, the current Prints and Photographs Online Catalog has advantages beyond a growing volume of content and the ability to serve remote users.
The modular design of the architecture that supports American Memory and the Prints and Photographs Online Catalog will permit incremental enhancements in response to changes in the technical environment and the expectations of users.