Abstract: Aspects of the subject matter described herein relate to customizing and aggregating catalogs. In aspects, a user configures a virtual catalog to be created from one or more other catalogs. The user may specify inclusion and exclusion rules that indicate what catalogs, categories, products, and variants to include or exclude in the virtual catalog. The user may also specify that certain properties be overridden in the virtual catalog. If desired, the virtual catalog may be materialized to improve performance or for other reasons. Changes that occur to derived from catalogs may be detected and used in rebuilding a virtual catalog.