In a traditional library or bookstore, one can browse along the shelves reading the titles of books and the names of authors and can flip the pages looking for items of interest. In a digital library, however, these clues are not available. Clearly there is a need for new types of document surrogates for use in digital libraries that would enable searchers to identify useful documents and decide what objects to examine next. The authors “present a framework for the design of information representations [in digital libraries] in terms of previews and overviews” (p. 380). “Previews and overviews are graphic or textual representations of objects of interest.” A preview “acts as a surrogate for a single object of interest,” while an overview “represents a collection of objects of interest” (p. 381).

A set of eight design guidelines is provided to help designers apply the preview and overview concepts to various information retrieval projects. Three applications are described in some detail: the NASA query preview project; the Library of Congress National Digital Library Prototype Program; and the LifeLines interface, which is designed for retrieving information from a large collection of personal history records about delinquent youths. Descriptions of these studies are accompanied by photographs of displays retrieved from the databases or document collections. These descriptions indicate the value of using multiple surrogates to reveal details of the contents while allowing users to customize the displays.

With the growth of digital library collections, it is extremely important to inform users of “the full range of data attributes common across the site so that users can see basic organizational schemes and gain a general sense of what is and what is not available in the library” (p. 391). The proposed previews and overviews provide such a framework, and they should be studied, applied, and tested.