Rich visual databases of buildings and places will oon become available in electronic form. Already most niversities are digitizing their slide collections and as copyright issues are sorted out, image collections will become available on CD-ROM and over the world networks. Several research prototypes have examined interfaces and applications for computer-based visual collections(Bakergem 1990; Clayton and Wiesenthal 1991), and at least one digital library of architectural images, the Great Buildings Collection, is commercially available on CD-ROM (Matthews 1994). However
little work has been done to integrate these collections into computer based design processes, or on extending traditional keyword schemes to index them.

The traditional twentieth century architectural visual database--the slide library--is indexed by a list of keywords, which identify images of buildings and places by name, geographic location, architect, date built, as well as building type and style. Sophisticated indexing schemes such as the Getty Art and Architecture Thesaurus (AAT) provide detailed
ways to characterize features of buildings (Getty Trust 1990). However they require of users a great deal of knowledge about the index categories and subcategories. Ultimately these schemes are based on key word search of a text index.

This paper explores the feasibility of a diagram-based visual query scheme to index visual databases for architectural design. In this scheme, an automated visual librarian program finds items in the catalog that match--more or less--a hand drawn diagrammatic query. The paper describes work toward this goal, presenting the results of two pilot experiments and a working prototype of a diagram based retrieval program. The paper is arranged as follows: First, the
introduction reviews related work on visual query systems, describes ways slide libraries are currently used, and considers new uses that diagram-based indexing might make possible. The second section describes two pilot experiments that suggest there is enough similarity among architects' diagrams of designs to make diagram based indexing feasible. The third section argues that diagram based indexing is also technically feasible. It presents an `Electronic Cocktail Napkin' program that recognizes hand drawn diagrams, and describes its mechanisms for graphical
search and retrieval. The fourth section describes the application of the Cocktail Napkin program to build a working prototype of a visual librarian. The paper concludes with a discussion of lessons learned and scale-up problems, and outline directions for further work.

Electronic Cocktail Napkin