Virtual shelves. II: A unified catalog for a heterogeneous collection.

We describe a unified catalog of traditional and digital resources in medical informatics, using standard cataloging principles (AACR2), schemes (LCC), and coding formats (USMARC). The unified catalog integrates the bibliographic records of physical items in the heterogeneous collection with the bibliographic records of network accessible digital items, using prescribed cataloging formats to new effect. The unified catalog is collections-based. We do not use the MARC 856 field to specify the network location of a digital item. The location of a digital item is determined by mapping its call number through a location guide to a network address. This mapping is strictly isomorphic to the way the shelf location of a physical item is determined within the bounds of a controlled collection.