On the Theory of Library Catalogs and Search Engines is a neat paper Supplementing the talk on "Principles and Goals of Cataloging", given at the German Librarians' Annual Conference Augsburg 2002. Eversberg, says Using Internet search engines, and knowing their operation is fully automated, people tend to view with skepticism all practical and theoretical effort invested in catalogs. Any good search engine, however, will always be based on a good theory - though that one may differ quite a bit from a catalog theory. He asks What is a good catalog? and What should catalogs do?