We present an architecture for electronic catalogs, called Smart Catalogs and Virtual Catalogs.  Smart catalogs are searchable, annotated combinations of machine-readable (i.e., minimally processable) and machine-sensible (i.e., actually understood by the computer) product data.  Virtual catalogs dynamically retrieve information from multiple smart catalogs and present this product data in a unified manner with its own look and feel, not that of the source
smart catalogs.  These virtual catalogs do not store product data from smart catalogs directly (except when caching for performance); instead virtual catalogs obtain current product data from smart catalogs to satisfy specific customer queries.  Customers interact with smart catalogs and virtual catalogs through WWW or other interfaces.

Virtual Catalogs are built using a system called Infomaster.  Some other examples using Infomaster can be found at http://infomaster.stanford.edu, and there are some papers available from there as well.