1. A system providing seller pre-qualification during the matching phase of an electronic commerce transaction, comprising: a directory structure comprising a plurality of hierarchically organized product classes, each product class categorizing a plurality of products and defining one or more attributes of the products categorized in the product class; one or more pointers for each product class, each pointer identifying a seller database in which product data enabling a product transaction is stored for products categorized in the product class, each seller database associated with a seller having values for one or more seller attributes; and a search interface operable to communicate, in response to selection of a product class and specification of one or more seller attribute criteria, a search query for product data only to one or more seller databases associated with sellers having seller attribute values matching the specified seller attribute criteria, these seller databases being identified by the one or more pointers associated with the selected product class.